In anticipation of tonight’s debate, we partnered with Ipsos and The Washington Post to ask likely Republican primary voters what they think about tonight’s debate participants and the candidate field in general.

The 4,968 likely Republican primary voters we polled using Ipsos’s KnowledgePanel expect Ramaswamy’s performance to be best among the eight expected debate participants. According to a five-point scale that we calculated using respondents’ answers (with 1 being “terrible” and 5 being “excellent”), likely voters expected Ramaswamy to perform “very good” (3.59 out of 5). They thought DeSantis would perform second-best (3.51 out of 5) and Scott third (3.43 out of 5).

When it comes to whom respondents think they’ll place their votes for in the primaries, 65 percent are considering Trump and 52 percent are considering DeSantis. About 1 in 4 likely Republican primary voters are considering voting for Pence, Scott and Haley. The remaining six candidates we asked about fell below 25 percent.

We’ll be watching to see how the candidates fare tonight, and if debate watchers’ opinions on whom they’re considering voting for will change after tonight’s performances.

-Analysis by Holly Fuong of FiveThirtyEight

Before tonight’s debate kicks off, FiveThirtyEight, The Washington Post and Ipsos partnered to ask Republican voters about how they might vote in the upcoming Republican presidential primaries. Specifically, we asked 4,968 likely Republican voters which issues are most important to them when deciding which candidate to vote for in the primaries, using Ipsos’s KnowledgePanel.

We offered respondents a list of 16 issues and allowed them to select up to three. Of the topics that we asked about, voters were most concerned about “getting inflation or increasing costs under control” (53 percent of respondents selected this issue), something Republican voters have been concerned about since at least the 2022 midterms, according to a previous FiveThirtyEight/Ipsos poll. Other issues that were top of mind for voters were “controlling immigration” (36 percent), “someone fighting against liberalism and the woke agenda” (25 percent) and “ability to beat Joe Biden” (25 percent).

If tonight’s debate touches upon those top issues, voters might get some clarity on who they are considering voting for when primary season comes around.

-Analysis by Holly Fuong of FiveThirtyEight

At PolitiFact, this is our fifth presidential cycle. We’ve published more than 23,000 fact-checks since launching in 2007, all using our Truth-O-Meter, which rates claims on a scale from True to Pants on Fire false for the most ridiculous claims.

If PolitiFact is new to you, there are a couple of rules of the road.

First, we don’t fact-check every claim every candidate says. We couldn’t … we’d be dead.

We focus on claims that are particularly interesting, in the news or obviously potentially wrong. Our grading scale tries to measure both the literal truth and how voters might interpret a politicians’ words. So if Pence tonight claims that he and Trump “achieved energy independence” in their first three years in office, it can be more complicated to fact-check than you think.

In Pence’s case, yes, the United States did produce more energy than its citizens consumed during the Trump/Pence White House, but that was built on more than a decade of improvements in shale oil and gas production, as well as renewables. And the U.S. did not produce more gasoline than it consumed (which is maybe what you were thinking about). And if that’s not enough, even though the U.S. didn’t use all the energy it produced, it still imported a substantial amount of energy to serve domestic markets.

So far in this cycle, we’ve published 52 fact-checks of the GOP candidates. Our checks tend to follow the polling of the race. We’ve fact-checked Trump 17 times, DeSantis 14 times, Pence six times, Haley and Tim Scott each five times, and so on. We'll be drawing on those previous fact-checks, as well as the thousands of other claims we've vetted, throughout the night.

-Aaron Sharockman, PolitiFact

I flew to Milwaukee earlier this week to talk to some local voters and learn more about why the GOP decided to have its first presidential debate of the 2024 cycle in the state.

-Analysis by Galen Druke of FiveThirtyEight

Trump maintains a lead of 25 percentage points over his nearest competitor in Iowa, according to the latest polls.

DeSantis and Scott are both polling higher in Iowa than they are nationally, according to our polling average. Trump is polling about 10 points lower in Iowa than in national polls.

According to a July poll from J.L. Partners/DailyMail.com, only 51 percent of Iowa Republicans said their mind was made up. Forty-three percent said they could still be persuaded to support another candidate. Voters who said they plan to vote for Trump were the most likely to say their mind is made up, with 80 percent saying so compared with 37 percent of those who said they plan to vote for DeSantis and 11 percent of those who said they plan to vote for Scott.

Scott and DeSantis have the highest net favorability among Iowa Republican voters. Pence, Christie and Hutchinson are underwater.

In an early state poll from the Manhattan Institute conducted in July, Iowa Republicans are split on whether electability is important. Forty-six percent of Iowa Republican voters say that it is most important for Republican candidates to win elections and be in power, even if that means compromising or moderating their positions, while 45 percent said it is most important for candidates to stay true to their principles, even if that means losing elections.

Iowa Republicans also think that skipping primary debates shows weakness more than strength, according to a July Fox Business/Beacon Research/Shaw & Co. Research survey. Fifty-nine percent of Republicans said skipping the debate shows weakness, while 27 percent said it shows strength.

-Analysis by FiveThirtyEight