Three weeks after the first Republican presidential primary debate, the latest Fox News survey finds Donald Trump has increased both his lead in the race and his strength of support. 

Sixty percent of Republican primary voters back Trump in the primary race, up from 53% in the Fox News pre-debate August survey.

Trump did not participate in the August 23 GOP debate hosted by Fox News.

At 13% support, Ron DeSantis sees a downtick of 3 points since the debate, while Vivek Ramaswamy holds steady at 11%. Next is Nikki Haley with 5%, Mike Pence and Tim Scott at 3% each, and Chris Christie at 2%.  All remaining candidates receive 1% or less.

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Fox News poll on GOP primary

A Fox News poll on candidate preference in the Republican presidential primaries. (Fox News)

Some of Trump’s biggest gains come from women (+10), voters under age 45 (+9), White evangelicals (+8), and White men without a college degree (+8).

DeSantis lags notably among women, he’s down 8 points with them since August.

"Unless something changes, this is Trump’s race to lose," says Republican pollster Daron Shaw who conducts the Fox News Poll with Democrat Chris Anderson. "The question is, how likely is it that something changes enough to shake Trump’s Republican supporters loose and get them to look at someone else?"

The survey also asks voters their second-choice candidate, which gives us an idea of what would happen if someone were to drop out. For example, without Trump, the poll shows a tight race between DeSantis and Ramaswamy, at 33% and 31% respectively, with Pence in third at 11%.  All others are in single digits in that scenario.

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Fox News poll GOP primary

A Fox News poll on GOP primary preference without former President Trump in the race. (Fox News)

Another indication of Trump’s strength is the growing number of GOP primary voters saying they will definitely back him – now 65%, up from 58% in June.

Fox News poll GOP primary

A Fox News poll on GOP presidential candidate preference.  (Fox News)

That level of support isn’t seen for any other candidate tested: 28% say they definitely will back DeSantis, 24% for Ramaswamy, 13% for Haley, 12% for Scott, 9% Pence, and 4% Christie.

Ramaswamy (+11) and Haley (+3) are the only candidates, besides Trump, who enjoy a bump in the percentage saying they will definitely support them. 

Christie wins the unwanted honor of having the highest share saying they would never support him (53%). That’s up almost 20 points since the question was last asked in the run-up to the 2016 election, when 34% said they would never vote for him in that election (August 2015).

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Next is Pence, with a "never" number of 40%, up from 35% pre-debate. He is followed by Haley (24% vs. 20% pre-debate), DeSantis (16% vs. 14%), Ramaswamy (15% vs. 16%), Scott (15% vs. 16%), and Trump (11% vs. 13%).

Since the GOP debate, Ramaswamy (+8 points), Haley (+6), Trump (+4), and Burgum (+2 points) all saw increases in their favorable rating among GOP primary voters while DeSantis (-2), Scott (-2), and Christie (-1) saw declines. Pence saw no change. 

GOP presidential debate

FOX News Media’s "Democracy 24: FOX News Republican Primary Debate" drew a staggering 12.8 million total viewers. (Al Drago/Bloomberg via Getty Images)

While Ramaswamy’s favorable number improved, so did his unfavorable and not just among GOP primary voters (+3) but also among all voters (+12). 

Haley saw a 9-point increase in favorability overall, while her unfavorable number held steady. 

"Support for Trump is so strong in the Republican primary that any signs of growth among his rivals also spurs backlash among Trump loyalists," says Anderson. "It’s increasingly difficult to see a winning pathway out of primary for anyone not named Trump."

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The next Republican debate is Wednesday, September 27 hosted by Fox Business Channel.

Equal numbers say they will participate in the Democratic and GOP primary or caucus in their state (40% each). 

President Biden has also widened his lead in the Democratic presidential primary race:  71% of Democratic primary voters back him, up from 64% in August. Robert F. Kennedy Jr. receives 17%, while Marianne Williamson garners 6%.

Fox News poll Democratic primary

A Fox News poll on the Democratic presidential primary race. (Fox News)

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Conducted September 9-12, 2023, under the joint direction of Beacon Research (D) and Shaw & Company Research (R), this Fox News Poll includes interviews with 1,012 registered voters nationwide who were randomly selected from a voter file and spoke with live interviewers on both landlines and cellphones. The poll has a margin of sampling error of plus or minus 3 percentage points for all registered voters and plus or minus 5 points for Democratic and 4.5 for Republican primary voters.