Sen. Marco Rubio (R-Fla.) greets supporters at a primary election partyin August in Kissimmee. (John Raoux/AP)

At the end of Sen. Marco Rubio’s 40-minute talk to Jewish voters here, a young member of the Boca Raton Synagogue asked the awkward question. Could Rubio comment on “the trajectory of the GOP” after November?

“No, I have no idea what’s going to happen,” Rubio said. “Look, I’ve been wrong in my projections so far.”

Everybody got the joke. Had the presidential primaries gone another way — had Rubio not spent the run-up to Super Tuesday joking about Donald Trump’s hand size and flop sweat, he might be the Republican nominee for president.

“He’d be up 10 points” against Democratic nominee Hillary Clinton, sighed Anthony Di Perna, a reluctant Trump voter.

Instead, Rubio is running for the Senate again — and trying to protect a lead as Trump brings rubble down around him. In Rubio’s telling, in speeches and in Monday’s first televised debate, the election is a choice between “two deeply flawed candidates,” and the worst thing a voter could do would be to register his disgust down ballot by voting for Democrats.

U.S. Rep. Patrick Murphy (D-Fla.) celebrates in Palm Beach Gardens in August after winning the Democratic primary to challenge Sen. Marco Rubio for his Senate seat.. (Richard Graulich/AP)

Rubio has maintained a single-digit advantage over Rep. Patrick Murphy (D-Fla.), a moderate Treasure Coast Democrat who was recruited by the national party after Rubio’s original pledge to leave the Senate.

Democrats’ hopes dimmed after Rubio decided to run for reelection to the Senate after all. But now, they are asking if Trump’s toxicity — and Rubio’s delicate dance with the candidate at the top of the ticket — can put Florida back into play. Rubio has endorsed Trump, but he has avoided appearances with him and media inquiries.

At Monday’s debate, Rubio offered himself as a senator who shared the sour feelings of the swing voter — never mind his endorsement of Trump. Onstage, Rubio goaded Murphy for overstating his CPA credentials. On social media, Rubio’s team worked to turn Murphy’s attempt at focusing on the Trump endorsement — “Let’s talk about Donald Trump again” — into a desperate gaffe.

By Tuesday morning, that team was declaring victory. The Democratic Senatorial Campaign Committee canceled its ad buy. Rubio’s presidential bid had ended in a humiliating, home-state loss to Donald Trump. But voters knew him. They did not know Murphy. The same strategists who had drafted Murphy into an open race had perhaps found the limits of the anti-Trump backlash.

“We have a senator who’s putting his own political ambition ahead of what’s best for Florida,” Murphy said in an interview. “Most leaders in the party have not only disavowed Trump, but unendorsed him. Sixteen senators have had the courage to unendorse him. Not Marco Rubio. He doubled down.”

Recruited, touted and funded by the DSCC, Murphy spent the weeks before the Trump implosion explaining why that group and a related super PAC had already started to scrap $6 million of $10 million in planned ad buys. He had $4 million left to spend, just $600,000 less than the incumbent. Rubio’s line that “both candidates” were flawed skipped over Clinton’s higher favorable ratings — still underwater, but not as toxic in Florida as Trump.

And Democrats, who a month earlier had despaired about beating Rubio, began the week looking for an opening — a path to the Senate laid by angry Trump voters leaving the rest of their ballots blank.

At a debate against Democratic rival Patrick Murphy, Oct. 17, Sen. Marco Rubio (R-Fla.) explained why he believes U.S. elections aren't "rigged," contrary to what GOP presidential nominee Donald Trump says. (WFTV)

Not everyone has declared the race over. Last week, Sen. Chris Murphy (D-Conn.) flew into Orlando to join Murphy and local candidates for Congress at a news conference commemorating four months since the Pulse nightclub shootings.

“I spent the morning on the phone calling my donors and national donors, telling them to put money into Florida,” Chris Murphy said. “I think Trump is the kiss of death for down-ballot candidates no matter what you do. If you don’t pull your support, you’re going to get asked questions about why you’re sticking with this monster.”

Rubio’s campaign, which has outraised and outspent Patrick Murphy, is trying to play confident without exposing the candidate to risk. In the week after The Washington Post obtained a tape of Trump bragging about an unwanted advance on a married woman, Rubio held no events that were announced to the news media. The senator reaffirmed his support for Trump in a statement; in public, he focused more on quick visits to areas damaged by Hurricane Matthew.

Meanwhile, Trump was barnstorming Florida with some of the most brazen speeches of his campaign. At one rally in Pensacola, he absolved Rubio of his primary attacks. “We like Marco,” Trump said quickly. But as he worked his way down the state, Trump accused House Speaker Paul D. Ryan (R-Wis.) of undermining him, seemingly mocked the looks of a People magazine writer who had accused him of pinning her against a wall and kissing her, and hinted that an international conspiracy was trying to rig the election against him.

Trump’s Thursday rally took place just 30 minutes from the Boca Raton event, and a few attendees could be heard debating whether they could speed down there in time to catch the nominee. Meanwhile, at the rallies themselves, by far the biggest happenings in Republican politics, enthusiasm for Rubio is hard to find — even among voters who intend to support him.

“I had to dig very deep,” admitted James Tomlinson, 59, an Army retiree who attended Trump’s rally in Lakeland. “Oh, I did a lot of soul searching on that one. A lot. And I was going back and forth: Vote for him. Don’t vote for him. Vote for him. Don’t. But I did. But I tell you, if he pulls another stunt like he did, he’ll never get my vote again.

The “stunt,” Tomlinson explained, was Rubio’s role in the failed immigration reform debate — something ignored completely in the Senate race. At Trump’s rally in Panama City Beach, Marla Clark, a 52-year old assistant at a law firm, said she had wrestled with whether to vote for a senator who had not “impressed” her and had lost her vote in the primary.

“I mean, I have to, because my vote counts,” she said. “But I need to sit down and really figure it out, because Florida was not impressed with Marco Rubio.”

A big problem for Murphy — one that the ads were supposed to solve — is name recognition. In the polls where he runs strongest, up to 30 percent of voters still have no opinion of Murphy. On Thursday, after the Rubio and Trump events in Boca, The Washington Post accompanied Democratic volunteers as they registered people to vote at nearby Florida Atlantic University, where the only voters who knew Murphy’s name were college Democrats.

More often, asked about the Senate race, voters talked about it as a static and confusing choice unrelated to the Trump-Clinton race. Paul Nagib, 19, said he was backing Trump because of what he’d read about the Democratic nominee in the book “Clinton Cash.” He had no opinion of the Senate race.

“I really have to read up on it,” he admitted.

“I haven’t paid attention,” said Zach Goosens, 24, who admitted he was likely to not vote at all because “the candidates we’re being forced to pick from” were so disagreeable.

In the race that Democrats expected, this might not have been an issue. Murphy was recruited when the Republican nominee looked to be one out of a half-dozen obscure GOP officials, from a Pinellas County congressman to the state’s lieutenant governor. Speaking about the race, several Republican strategists suggested that Murphy would be winning if he were a “generic D” facing off against a Trump-flummoxed generic Republican.

Since winning his swing district in 2012, Murphy had prepared for such a race. In Boca Raton, Rubio told voters that he was “the only candidate who has been critical of the nominees of both parties.” But Murphy had alienated some progressives — a problem that fizzled when his primary opponent Alan Grayson imploded — by talking up “structural changes” to Social Security and Medicare. He’d been one of very few Democrats to vote to create the Select Committee on Benghazi.

Asked about that vote this week, Murphy said it was to his credit, and he swung at Rubio for not condemning Trump’s call for a special prosecutor against Clinton.

“I have one of the most independent voting records in the country,” Murphy said. “That’s my pledge to everybody — I’m going to continue doing what’s best for Florida. But those accusations and threats to imprison your political opponent sound a lot like what Nicolás Maduro says in Venezuela, a lot like what Fidel Castro says in Cuba. I’ve had numerous phone calls with people from around the state, asking me, ‘Wait a minute, hasn’t Marco Rubio made a career on being against Castro and what happened in Cuba?’”

Rubio’s campaign, which has had little to say to reporters recently, has not engaged with this. The Rubio who is showing up is looking past November — and hoping voters will do the same.

“We’ve always had a discourse in this country that’s been heated when it comes to politics,” Rubio said in Boca Raton. “But we didn’t hate each other. It’s unbelievable: People literally hate each other.”

Jenna Johnson and Philip Rucker contributed to this report.