Pacing a makeshift stage in the parking lot of an electrical supply company in the sprawling suburbs around Tampa Bay, Marco Rubio has all the earnestness of an overeager undergrad with important things to say.
If Donald Trump wins the presidential nomination race, "it will fracture the Republican Party," he warns. Scuffles between Mr. Trump's supporters and protesters at rallies "make America look like a Third World country," he laments. The bellicose billionaire has turned American politics into "the comments sections of blogs … our politics have become Twitter trolls," he deplores.
"Who wants to live in a country where everyone hates each other?" he says to shouts of agreement from his audience. "Who wants to live in a country where everyone is at each other's throats over everything?"
Mr. Rubio has good reason to be so grave in his battle with Mr. Trump ahead of Tuesday's Florida primary: The home-state senator is fighting for his political life in what should have been a picnic. The Real Clear Politics average of polls has Mr. Trump ahead by a staggering 18 points here.
Mr. Rubio is pulling out all the stops. On Saturday alone, he held no fewer than five different events in the state; on Monday, he plans a frantic whistle-stop tour from Jacksonville to Miami.
It's astounding that it ever came to this. Mr. Rubio is the GOP's dream candidate: a youthful Latino from a swing state, and an effortlessly polished politician. At the parking lot rally, he speaks for more than 40 minutes without notes or a teleprompter, delivering a perfectly paced speech with numerous extemporaneous asides.
But this may exactly be Mr. Rubio's problem in the age of Trump.
"The media's helped Trump a lot; when he says these things that are completely unbecoming and he leverages off racism … the media flocks and photographs it and tapes it," says John Proni, a 43-year-old accountant standing in the crowd. "Marco doesn't do that."
Mr. Trump is so dominating the narrative here, Mr. Proni says, that children at his 11-year-old daughter's school began bullying a Hispanic girl.
"They were picking on her and telling her that she was going to have to leave the country when Donald Trump is president, and she started crying, and the other kids were shouting 'Trump! Trump! Trump!'" he says.
Mr. Proni isn't the only Rubio supporter who expresses horror at Mr. Trump's xenophobia.
While discussing Mr. Trump's plan to deport all of the United States' illegal immigrants, Marie King struggles to find a strong enough analogy.
"It's not feasible to deport 11 million people. It's ridiculous," the retired former NYPD officer says as she chats with friends after Mr. Rubio's rally.
"It would be like Hitler and the Nazis," interjects Tammy Freeman, 57, a nurse.
"Like Hitler and the Nazis – or like the Democrats during World War Two when they rounded up the Japanese," Ms. King says. "That's not the American way."
These sorts of comparisons are common here. And Mr. Trump's supporters do much to reinforce them.
Standing outside Mr. Trump's Tampa headquarters on the first floor of a converted cigar factory in a working-class Cuban neighbourhood, volunteer Albert Illes, 52, complains openly about seeing women in hijabs in the United States.
"They hate us. They do hate us. If you don't think they do, you've got a lot to learn," he says.
Mr. Illes says he's long voted Democrat, but soured on Mr. Obama for not taking a harder line with Iran and other Middle Eastern countries. And Mr. Rubio, he says, is a "scumbag" for having once worked as a lobbyist.
"The politicians in America are controlled by special interests and lobbyists. Donald Trump is not," he says. "He thinks from his heart."
Mireya Linsky, meanwhile, blamed immigrants for causing social problems in the country, including the disruptions at Mr. Trump's Chicago rally. An immigrant herself – Ms. Linsky came from Cuba as a child – she argues that anyone who comes over must come legally. "People coming here now … they want to take, take, take," she says.
"How he delivers [the message] sometimes can be a little bit out of the ball field. But it needed to be done. He needed to get attention to wake people up," she says.
Mr. Rubio, by contrast, has a rhetorical style that reminds of an honours student running for class president. When he's done being disappointed by Mr. Trump, he shifts to a litany of Boy Scout bromides.
"I believe with all my heart that if we are willing to do what needs to be done, our children, the young Americans who are here today, have a chance to be the freest and most prosperous Americans that have ever lived," he declares.
It's this sort of optimism that drew Rob Hartwell, a 59-year-old business development consultant, to volunteer for Mr. Rubio's campaign.
"Marco is the future of the Republican Party. He's young, he's vibrant, he's intelligent," he says. "He stands for unifying the party and bringing all Americans together."
But he concedes not everyone is responding well to that call for conciliation in the Sunshine State: "We see it out on the streets, we see it knocking door-to-door – some of the Trump people raise their middle finger to us. They want us to go away."
If that's anything to go by, Mr. Rubio may very soon be the Republican Party's past.