As former President Donald Trump finalizes his choice for a running mate, allies of Sen. Marco Rubio (R-FL), a top contender for the vice presidential slot, have argued that he would be a valuable addition to the ticket, citing his appeal to Latino voters, his ties to key donors and his foreign policy chops, among other draws.

But Rubio’s rise has also raised concerns among traditional GOP hawks and conservative pro-Israel foreign policy experts who once viewed the Cuban American senator as one of the strongest defenders of a muscular approach to international engagement that has struggled to compete with the ascendant populism dominating the party.

Now, some of his critics say, Rubio’s conversion from an erstwhile Trump critic to a MAGA ally has cast doubt on the sincerity of his commitment to the hawkish foreign policy vision he had long espoused, most notably as a presidential candidate in 2016, when was highly critical of Trump’s America First platform.

The main source of contention stems from Rubio’s vote in April against a $95 billion aid bill for Israel, Ukraine and Taiwan, which passed the Senate by an overwhelming margin. In a floor speech defending his vote, Rubio, who was once a leading advocate for protecting Ukraine, claimed he supported the aid in principle but chose to oppose it because of a lack of border security provisions, describing the bill as “legislative blackmail.”

The April vote was interpreted by Rubio’s congressional colleagues as an indication that he was adjusting his positions to align with Trump’s base in an effort to ingratiate himself with the former president’s campaign. A few months earlier, Rubio had also rejected a bipartisan compromise bill that included foreign aid and border security legislation after Trump had voiced his opposition.

Rubio’s evolving approach to Ukraine and Israel aid has angered some of his former allies in the national security community, including foreign policy advisers on his presidential campaign, who allege that he is irresponsibly playing politics on a crucial issue while abandoning core principles he once fiercely promoted.

Rubio, now 53, “was very much in the McCain and McConnell internationalist camp as a candidate for president in 2016,” one prominent former supporter who has served in Republican administrations told Jewish Insider earlier this week, referring to the late Sen. John McCain (R-AZ) and Senate Minority leader Mitch McConnell (R-KY). “The switch to a Trumpier line seems motivated partly by Trump’s influence on the party, and in that sense Rubio may be moving closer to the average Republican voter.”

“But it’s disappointing because he knows better,” added the former Rubio supporter, who like some others spoke on the condition of anonymity to weigh in more candidly. “His vote against help for Ukraine would have drawn scorn from the Rubio of 2016.”

Meanwhile, a GOP foreign policy expert with firsthand knowledge of Rubio’s thinking as a presidential candidate said he rejected the senator’s explanation for his vote against aid for Israel and Ukraine amid their respective battles with Hamas and Russia. “I personally was very disappointed he cast that vote — I don’t care what the reasons,” he said in an interview with JI on Wednesday, casting Rubio’s decision an “invitation to aggression” and a “form of appeasement.”

 “You can change your rhetoric, you can say different things, but when the rubber hits the road — and it did in that appropriation — then it’s very serious,” the foreign policy expert stressed. “I think Rubio understands the risks,” he speculated, “but his ambition is overtaking his judgment.”

A leading conservative foreign policy expert in Washington, D.C., who also once backed Rubio,  recalled the senator as a “solid internationalist” during his early years on the Hill, saying that he arrived “with a lot of potential.” But, the expert argued, “as the wind shifted, he suddenly became J.D. Vance light,” referencing the Republican senator from Ohio and veepstakes contender who, as a leading opponent of aiding Ukraine, has sought to pull the party in a more isolationist direction. “It’s so frustrating.”

A spokesperson for Rubio’s office did not respond to a request for comment from JI on Thursday.

Rubio has in recent years embraced a more hands-off approach to American engagement abroad, while advocating for a populist economic agenda that is focused on domestic production in an effort to counter China’s rise, which he has characterized as “just as great a threat as the Soviet Union ever was, if not an even greater one.”

Former Rep. Carlos Curbelo (R-FL), a moderate Republican who endorsed Rubio for president in 2016, said the senator remains a “firm believer in American global leadership,” even as “he has clearly responded to the concerns of a large portion of his political base regarding American investment overseas.”

“Republican voters have become more populist over the last 15 years and have compelled Republican members of Congress to focus more on domestic matters including fiscal concerns and working class voters’ struggles with cost of living,” Curbelo told JI earlier this week. “That certainly explains some of Rubio’s shifts toward a more guarded trade policy and his crusade to make a greater portion of the child tax credit refundable during the 2017 tax debate on the Hill.”

Ford O’Connell, a Republican strategist in South Florida, agreed that Rubio has adapted to what he described as a “global landscape that has changed dramatically in the last 10 years.”

“I think you see a situation where Rubio is evolving with it,” O’Connell said in an interview with JI on Wednesday. “What’s happened now is that China is seen as the preeminent threat and Republican foreign policy has also changed in the sense that America cannot be everywhere all the time. Endless wars are not in vogue, not only with Republicans but pretty much with the voters who will decide this election.”

In a brief interview with JI on Wednesday, Rubio, the vice chairman of the Senate Intelligence Committee, characterized his approach to foreign policy as “21st-century American strength,” noting that “the world looks different than it did five, 10, 15 years ago.”

“America faces a lot of challenges, and it has to be able to prioritize the ones that are most critical to our national security and our national interest,” he elaborated. “It doesn’t mean we don’t care. We want to see great outcomes everywhere in the world, but there are things we’d like to do and then there are things we have to do, and so I think that that’s the era we’re in now.”

Asked how Israel in particular fits into such calculations, Rubio called the Jewish state “the only pro-American, free enterprise democracy in the Middle East,” adding, “If we’re not going to support Israel, then no ally in the world would trust us.”

Despite his vote against the supplemental aid bill for Israel and Ukraine, Rubio has voiced consistent rhetorical support for Israel as well as continued arms transfers. He has also been among the most outspoken senators in warning of a regional threat from Iran and the possibility of full-scale war between Israel and Hezbollah, while pushing for stronger sanctions on Iran and Hamas. He has urged U.S. leaders to outline to the American public why such a war might be necessary.

Some of the GOP’s top pro-Israel donors have expressed comfort with the senator as a vice presidential pick, even as he voted against the foreign aid legislation that included funding for Israel just a few months ago. 

“I think he’d be a solid pick,” Barry Funt, a board member with the Republican Jewish Coalition, told JI in an interview last week, adding that he believed Rubio could help to expand Trump’s base of support in the November election. “That’s my focus.”

Eric Levine, a top GOP donor, likewise voiced support for Rubio over Vance, whose foreign policy views have drawn scrutiny from some pro-Israel activists.

In assessing Trump’s shortlist, some pro-Israel Republicans have also voiced their approval of North Dakota Gov. Doug Burgum, a traditional conservative who has backed continued aid to Ukraine and is among the contenders Trump is weighing for vice president. 

Even as Rubio had an antagonistic relationship with Trump during the 2016 election, exchanging a range of memorable insults, the senator enjoyed close ties to Trump’s White House, serving as a key adviser on Latin American policy, most notably including an aggressive push for new leadership in Venezuela.

But Rubio, who appeared alongside Trump at a rally in Miami on Tuesday, is now more emphatically leaning into his support for the former president — even as the Florida senator could be compelled to relocate to another state if he ultimately joins the ticket.

Aaron Friedberg, a national security expert who served as a foreign policy adviser to Rubio during his 2016 campaign, described the senator as a “shrewd, intelligent and ambitious politician who has adjusted many of his positions and his rhetoric to bring them more closely into alignment with Trump’s.”

“None of this is especially admirable or courageous and some of it — like toying with election denialism and refusing to commit to accepting the results of the 2024 campaign — is downright dangerous,” he said in an email to JI earlier this week, alluding to Rubio’s recent comments on the election. “At the same time, with the very important exception of funding for Ukraine, which he recently opposed, Rubio still seems to favor a strong, engaged U.S. posture in the world.”

The senator, he said, “continues to advocate a strong defense, talks about the importance of our alliances in Europe and Asia,” promotes “a tough stance against China” and “can’t fairly be described as an isolationist.”

Still, Friedberg, who served as a deputy national security adviser to former Vice President Dick Cheney, was less certain about how Rubio would defend such principles if he ends up serving in the White House. “Whether he’d stick to these positions as vice president or shed them if they put him at odds with Trump,” he noted, “remains to be seen.”

Additional reporting contributed by JI congressional correspondent Emily Jacobs and senior congressional correspondent Marc Rod.