Immigration is driving support for Trump more than in 2016

Former President Donald Trump's signature campaign issue of immigration immediately helped fuel his remarkable rise to the top of the Republican primary polls in 2015. In a 2018 study, political scientists John Sides, Lynn Vavreck and I found that negative views of immigrants were a strong and consistent predictor of Republicans' support for Trump in the primaries — from the very start of his campaign in June 2015 up until he formally accepted the GOP nomination in July 2016.

Attitudes toward immigration were also a much more potent factor in the 2016 primaries than they had been in prior Republican nominating contests. Unlike Trump, who powerfully tapped into a reservoir of anti-immigrant sentiment en route to winning the nomination, then-Sen. John McCain and former Massachusetts Gov. Mitt Romney both performed slightly better among pro-immigrant voters than they did with immigration hawks in the 2008 and 2012 GOP primaries, respectively.

As important as immigration was to Trump's 2016 success, though, it now appears to be an even stronger source of support for him in the 2024 primaries against former U.N. Ambassador Nikki Haley. Just look at the exit polls from New Hampshire:

Between 2016 and 2024, Trump's support remained relatively constant over the past eight years among New Hampshire primary voters who said that most undocumented immigrants should be offered a chance at legal status: He performed just 4 percentage points better with this group last Tuesday than he did in 2016 even though his overall vote share went up by nearly 20 points. However, Trump's support surged 25 points from 2016 to 2024 among New Hampshire primary voters who think most undocumented immigrants should be deported.

Trump's stronger showing among that group is further amplified by the rising share of Republicans who think undocumented immigrants in the U.S. should be deported. In the 2016 New Hampshire exit polls, only 41 percent of Republican primary voters said that most undocumented immigrants working in the U.S. should be deported. That increased to 55 percent in the 2024 exit polling data, which dovetails with the rising support for deportation among Republicans nationwide since Trump left office.

Republicans in both New Hampshire and throughout the country have increasingly prioritized the issue of immigration as well. Three out of every 10 voters in last week's Republican primary told exit pollsters immigration was their top issue — up from just 15 percent in 2016. Trump's share of the New Hampshire vote similarly surged among this growing group of GOP primary voters who are the most concerned about immigration — from 53 percent in 2016 to 79 percent in 2024.

There are undoubtedly many reasons why immigration seems to have been even more potent in Trump's win last Tuesday than it was in his 2016 New Hampshire victory. Some of it could certainly stem from the recent influx of news about the southern border. In fact, my research shows that media coverage can make attitudes about social groups such as immigrants matter more in elections. But perhaps the most important factor stems from the differing natures of both Trump's candidacy and the field of presidential candidates in this year's GOP primaries.

Some Republicans who shared Trump's negative views of immigrants may have still been reluctant to vote for him in 2016 because of concerns they had about his lack of experience, electability and presidential temperament. These GOP voters who weren't quite ready for Trump to be the nominee in 2016 still had the viable option of pulling the lever in the primaries for a candidate like Sen. Ted Cruz, who was running for the party's nomination as a fellow immigration hawk. And many did, as our analyses found that Cruz won almost a quarter of the vote against Trump among 2016 primary voters who had the least favorable views of immigrants.

In stark juxtaposition with that prior contest, however, Trump is now a seasoned presidential candidate who is campaigning for a third consecutive GOP nomination in a one-on-one race against a challenger who has more ambiguous positions on immigration than a hardliner like Cruz. Moreover, Trump has increasingly drawn negative attention to Haley's own background as the daughter of immigrants who came to the U.S. from India before she was born. Over the past month, he has repeatedly mocked her birth name, Nimarata, and baselessly questioned her birthright citizenship as an American who was born in South Carolina.

That head-to-head contrast with Haley has likely helped make immigration attitudes a stronger predictor of support for Trump in the 2024 Republican primaries than it was back in 2016. After all, Larry Bartels's venerable account of presidential primaries showed that, as voters acquire more information about candidates, "the public comes to increasingly evaluate candidates on their political merits, in accordance with longstanding political predispositions." Attitudes toward immigrants should therefore have become more strongly linked to support for Trump after he was increasingly contrasted with Haley during the New Hampshire primary campaign.

To be sure, New Hampshire is just one small state, and it remains to be seen how immigration attitudes will factor into Republicans' support for Trump throughout the election year. But any increased importance of immigration in the 2024 presidential primaries would only further solidify Trump's steadfast stranglehold on the Republican Party going forward.