Although the governor has not yet officially declared himself a candidate, he and Trump are the clear front runners in the Republican race. Both have dismissed US support for Ukraine and other allies as a waste of resources and said that leaders should pay more attention to issues at home.

On the other side, a slew of declared and likely Republican challengers - including former UN Ambassador Nikki Haley and Trump’s former vice president Mike Pence - have portrayed themselves as steadfast defenders of Ukraine, willing to stand up to US foes including Russia and China.

Caught in the middle is the Republican electorate, which is split on whether the US should support Ukraine and how the nation should engage with the world more generally, according to Reuters/Ipsos polling.

Once the party of foreign policy “hawks,” Republicans have increasingly cooled on foreign entanglements and military support for allies, particularly after Trump took office in 2016.

The ideological shift of the party - which led the US to war in Iraq and Afghanistan two decades ago - was laid bare on Monday when conservative television host Tucker Carlson posted on Twitter responses from Republican candidates and possible hopefuls to questions on the war in Ukraine.

“While the US has many vital national interests ... becoming further entangled in a territorial dispute between Ukraine and Russia is not one of them,” DeSantis said in his reply.

Some Republicans were quick to hit back.

In a statement on Tuesday, Haley reiterated her support for Ukraine. “America is far better off with a Ukrainian victory,” she wrote.

Republican senators Marco Rubio, who is from DeSantis’ home state, and Lindsey Graham, both former presidential candidates, criticised isolationists within their party.

“When it comes to Putin, you either pay now or pay later,” Graham wrote on Twitter, referring to Russian President Vladimir Putin.

“DeSantis’s comments very much recall the Republican pre-World War Two tradition of so-called isolationism, which was really an indifference to European security,” said Dan Fried, a former top State Department official under President George W. Bush who is now with the Atlantic Council think tank in Washington.

Party Split

Republican voters are divided on the issue.

In a Reuters/Ipsos poll in February, 55 per cent of Republicans said the United States should support democratic countries when they are attacked by non-democratic nations. Asked whether the US should continue sending weapons to Ukraine, self-identified Republicans were split 50-50.

“People care about foreign policy, but I think it’s kind of mixed on Ukraine funding,” said Trudy Caviness, a member of the Iowa Republican State Central Committee.

“What I’ve heard (from party members) is that we have to give them what we’ve promised so far and then move on.”

Pollsters, analysts and campaign aides interviewed by Reuters said that DeSantis’ embrace of a more isolationist approach could open the way for more hawkish candidates to appeal to the significant chunk of the Republican electorate that still prefers a more hands-on US foreign policy.

Several prospective candidates, including Haley, Pence and former Secretary of State Mike Pompeo have made their foreign policy experience a key part of their pitch to voters.

By embracing Trump’s hands-off brand of foreign policy, DeSantis risks turning off some of the white-collar Republicans that are most eager to move on from the former president.

While 46 per cent of non-college educated Republicans said the United States should provide weapons to Ukraine, some 59 per cent of those with a college degree said the US should provide arms to Ukraine, according to a Reuters/Ipsos poll in February.

However, many will be voting for personalities rather than policies, pollsters said. That will give the eventual winner of the Republican nomination significant power to shape the party’s foreign policy preferences going forward.

“I think leadership matters a great deal on issues where voters can be a little unsure what they think about them,” said Sarah Longwell, a Republican strategist.