Many Haley voters won't back Trump. They weren't going to anyway.

UPDATE (July 17, 2024, 10:55 a.m. Eastern): On Tuesday, July 16, former U.N. Ambassador Nikki Haley spoke at the Republican National Convention, telling the audience that former President Donald Trump has her "strong endorsement, period." This puts Haley in the same camp as most Republicans this year and once again signals how firmly the party has coalesced around Trump as their presidential nominee and standard-bearer, as we discussed in the article below back in March.

UPDATE (May 23, 2024, 11:04 a.m. Eastern): On Wednesday, May 22, former U.N. Ambassador Nikki Haley offered her tacit endorsement of former President Donald Trump in the 2024 general election, saying that she "will be voting for Trump" against President Joe Biden. As discussed below, however, most of her Republican supporters were likely to vote for Trump anyway.On Tuesday, July 16, former U.N. Ambassador Nikki Haley spoke at the Republican National Convention, telling the audience that former President Donald Trump has her "strong endorsement, period." This puts Haley in the same camp as most Republicans this year and once again signals how firmly the party has coalesced around Trump as their presidential nominee and standard-bearer, as we discussed in the article below back in March.

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ORIGINAL ARTICLE (March 14, 2024, 5:38 p.m. Eastern): The Rolling Stones's "You Can't Always Get What You Want" has long served as one of former President Donald Trump's favorite campaign theme songs. But having sewn up the Republican presidential nomination last week, it's possible Trump's campaign needs to start humming a different late '60s tune: The Beatles's "Come Together."

After all, much ink has been spilled over whether supporters of former U.N. Ambassador Nikki Haley will back Trump in November. At first blush, there are certainly warning signs for Trump. For instance, Super Tuesday exit polls in California, North Carolina and Virginia found that between 80 percent and 95 percent of Haley primary voters in those states would be "dissatisfied" if Trump won the nomination. And an early March survey by Emerson College found that 63 percent of Haley backers preferred President Joe Biden over Trump in a general election matchup, compared to 27 percent who preferred Trump.

However, the prospect of Republican support coalescing around Trump may not simply be a function of whether he makes overt efforts to win over those Haley voters. Broadly speaking, results from past elections suggest that many of Haley's supporters will eventually line up behind Trump: Specifically, self-identified Republicans and independents who lean toward the GOP are very likely to "come home" to their preferred party's nominee. And while it's quite possible that many of Haley's more moderate independent supporters won't back Trump in the end, many within this sizable second group were never likely to vote for Trump in the first place — a pattern we've sometimes seen pop up in other recent nomination races.

Many Haley voters were unlikely to ever vote for Trump

For all the talk about Haley voters and the general election, we need to be careful about how much her performance says about potential divisions within the GOP. First off, Trump has won 72 percent of the Republican primary vote this cycle versus Haley's 24 percent, so Haley's voters constitute a clear minority of the GOP primary electorate. Only about half of her voters identified as Republicans, while the rest identified as independents or even Democrats, based on exit poll data. And based on their party identification, ideological views and attitudes toward Biden, it's apparent that a significant chunk of Haley supporters were more likely to vote for Biden than Trump in a general election in the first place. By comparison, Trump's primary voters more closely reflect the makeup of the GOP in terms of their party identification and conservative leanings.

Let's start with party identification, a telling indicator because voters who identify with a party or lean toward it (if they're independent) are very likely to support that party in the general election. Across the six states for which we have entrance and exit poll data — California, Iowa, New Hampshire, North Carolina, South Carolina and Virginia — just under half of Haley's voters identified as Republican, compared with 73 percent of Trump's supporters. Meanwhile, 41 percent of Haley's backers versus 27 percent of Trump's identified as independent or something else. Additionally, about 11 percent of Haley primary voters in those states — compared to virtually none of Trump's voters — identified as Democrats, a group that will mostly back Biden in November.

We don't have a breakdown of which party these independent voters leaned toward (the exit polls didn't ask), but based on their ideological views, we can deduce a significant gap between the independents who voted for Trump and those who voted for Haley. Across those six states, 71 percent of Trump independents identified as conservative, making it likely that most leaned toward the GOP. By comparison, 67 percent of Haley independents identified as moderate or liberal (to be clear, there were very few of the latter). Considering most independents lean toward one party, there are almost certainly a fair number of Democratic-leaning voters among the group of Haley independents who identified as moderate rather than conservative.

Biden's approval rating among Haley and Trump voters provides further evidence that Haley had significant backing from Democratic-leaning voters who participated in the Republican primary. Across the Super Tuesday exit polls from California, North Carolina and Virginia, 40 percent of Haley supporters approved of Biden's job performance as president, compared with just 1 percent of Trump voters. And among Haley backers in those three states who identified as independent, nearly half approved of Biden.

This approval rating among Haley voters is remarkably high given that, based on a basic polling average,* slightly fewer than 10 percent of Republicans and around 30 percent of independents nationally approve of Biden's job performance. By comparison, a little more than 75 percent of Democrats approve of Biden. All of this suggests a decent share of independent (or Democratic) likely Biden voters cast primary votes for Haley. Notably, this doesn't necessarily signal an anti-Trump shift for those voters: recent surveys from Emerson College and Siena College/New York Times suggest that a majority or plurality of Haley supporters voted for Biden in 2020.

Biden's approval ratings can also tell us something about the potential for how many Haley-supporting Republicans might defect and vote for Biden in the fall. Overall, only 1 in 4 of them approved of the incumbent president's performance across the three Super Tuesday states with exit polls. That's a higher percentage than Republicans nationally, but still suggests that most, even if they dislike Trump, will eventually default to their party identification and vote for him because they dislike Biden as well.

What past primaries say about breaking with the party

Taking what we know about the makeup of Trump and Haley primary voters, we can use data from past primaries to shed light on which ones tend to "come home" to the party's nominee and which tend to move into the opposition's camp in November. In 2016, both parties had lengthy, combative primaries that frayed support for the eventual nominees, based on validated voters who voted in both the primary and general elections in the 2016 Cooperative Election Study, a 50,000-plus person survey conducted by Harvard University in conjunction with YouGov. As the chart below shows, a meaningful share of primary voters who backed Vermont Sen. Bernie Sanders in the Democratic primary, or Florida Sen. Marco Rubio and then-Ohio Gov. John Kasich in the GOP contest, ended up voting for the other party's nominee.

While we shouldn't take these particular estimates as gospel — other survey findings differ at least to a small extent — the CES data suggests that around 1 in 10 Sanders voters went for Trump, while a similar share of Rubio voters backed Hillary Clinton, the Democratic nominee. Even more strikingly, around one-third of Kasich voters split for Clinton in November. (Though it's worth remembering that Sanders's sample size is larger — he won a lot more primary votes in a contest that lasted until June 2016 than Rubio and Kasich did before they dropped out in mid-March and early May of that year, respectively.)

On their face, such shares could add up to sizable general election vote totals — even enough to swing an election. For instance, state-level estimates from the same CES data suggested there may have been more Sanders-Trump voters in Michigan, Pennsylvania and Wisconsin than the final general election margins in those states — although accounting for Kasich-Clinton and Rubio-Clinton voters would complicate that math if we had sufficient sample sizes to estimate them at the state level.

But like many Haley voters this year, a fair number of Sanders, Rubio and Kasich voters were unlikely to vote for their primary party's eventual nominee to begin with. Just consider the party identification of primary voters who backed those three 2016 candidates compared to who they supported in the general electron. A decent chunk of primary voters who backed the opposite party identified with or leaned toward that party, whereas those who stuck with the party whose primary they voted in overwhelmingly identified with that party or leaned toward it.

All told, these numbers point to the likelihood that most Haley primary voters (or Haley supporters in polls) who identify as or lean Republican will go to Trump in November. Tellingly, more than 9 in 10 Sanders primary voters who eventually backed Clinton identified with or leaned toward the Democratic Party, whereas slightly less than half of Sanders backers who voted for Trump said the same. A similar share of Rubio and Kasich primary voters who ultimately voted for Trump in November were Republicans or GOP leaners. By contrast, only about 2 in 3 Rubio-Clinton voters and 2 in 5 Kasich-Clinton voters identified with or leaned toward the GOP. And it's worth reiterating that these defectors, who split from their preferred party's eventual nominee, constituted a very small minority of that party's primary voters.

Outside of those voters, each of these three candidates, much like Haley, won a sizable number of voters who identified as independent and/or preferred the other party — voters who were less likely to support the primary party's eventual nominee anyway. While it's not an apples-to-apples comparison, Kasich's 2016 numbers seem most likely to mirror what the 2024 exit polls suggest about Haley supporters. Overall, a whopping 40 percent of Kasich-Clinton voters identified as or leaned Democratic, making it little wonder that around one-third of all Kasich voters backed Clinton in November 2016. It seems clear that a sizable number of the Democratic-leaning voters who chose to participate in that year's Republican nomination race voted for Kasich, who stayed in the 2016 GOP contest for a month and a half longer than Rubio.

A look at how 2016 primary voters cast general election ballots based on their ideological views adds further evidence that many moderate voters in this year's GOP primary could be Democratic-leaning. Much like this year's Haley voters, per exit poll numbers, half of Kasich voters described themselves as moderate, and, remarkably, that group broke for Clinton 51 percent to 36 percent. Meanwhile, about one-third of Rubio's voters labeled themselves as moderate, and they only went for Trump 55 percent to 30 percent. (For both candidates, the remaining moderates largely backed Libertarian Gary Johnson.)

Now, Trump was certainly a shock to the system in 2016, accelerating political trends by pulling more white voters without a college degree into the GOP fold and pushing many college graduates toward the Democrats. Speaking to this, perhaps 6.7 million (or more) Trump voters had backed Democratic President Barack Obama in the 2012 election, and perhaps 2.7 million Clinton voters had previously backed GOP nominee Mitt Romney, based on a University of Virginia Center for Politics analysis. So, at least some primary voters' party identification as a Democrat or Republican could have been in flux that year. Nevertheless, there's little doubt that many voters who were unlikely to support Clinton in the general voted for Sanders in the primary, and many who were unlikely to support Trump in November voted for candidates like Rubio and Kasich. Perhaps tellingly, the combined 2016 vote share for Rubio and Kasich in primary states voting on Super Tuesday strongly aligned with Haley's vote share (a correlation of 0.89) in the 2024 GOP contest.

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For his part, Biden does have some experience consolidating support among those in his party. We don't have the same large-sample, validated-voter survey data for the 2020 Democratic presidential primary, but there is reason to think that most voters who supported one of Biden's primary opponents wound up supporting the Democratic nominee that November. For instance, Siena College/New York Times polling in June 2020 found that 96 percent who had preferred Massachusetts Sen. Elizabeth Warren, 92 percent who supported South Bend, Indiana, Mayor Pete Buttigieg and 87 percent of Sanders supporters said they would vote for Biden.

Whether this is suggestive of more unity among 2020 Democrats than 2024 Republicans is difficult to say. However, given the historical voting preferences of voters who identify with or lean toward a party, it's a reasonable bet that by June 2024 most Republicans and GOP-leaning independents will back Trump.

The same could also be true for Biden and most Democratic-leaning voters. While the incumbent president has faced no serious competition for his party's nomination — he's won about 86 percent of the primary vote this cycle — between 10 and 20 percent backed "uncommitted" ballot options in Michigan, Minnesota and North Carolina over the last couple of weeks, signaling some dissatisfaction with Biden.

But just as the Republican primary vote doesn't necessarily tell us much about how unified or divided the GOP electorate is, we should be careful not to overanalyze vote returns from a low-turnout, largely uncompetitive presidential primary on the Democratic side of the aisle. The more useful story can be found in the polls, where Biden has an approval rating at 38 percent and trails Trump by a small margin in general election polls.

Footnotes

*Biden approval averages by party affiliation were calculated using the line of best fit as a loess curve for each crosstab.