Signatures from Rubio supporters on a poster at his campaign headquarters in Miami. (Lynne Sladky/AP)

As local residents streamed into the West Dade Regional Library to vote early on Sunday, one of Marco Rubio’s volunteers instructed another in Spanish, “Seguir rezando” — keep praying.

A few steps away, Teresa Perez sat in her wheelchair wearing a white “Marco Rubio” baseball cap and holding a massive “Marco Rubio” poster.

“I’m here, and my mom is dying right now. But we have to help Marco,” she said as she fought back tears. Her mother has Alzheimer’s disease.

Perez sat from 7 a.m. to 4 p.m. Saturday and Sunday in the library parking lot hoping that shouts of “Marco! Rubio! Marco! Rubio!” could convince last-minute deciders.

Perez is heartbroken, unable to comprehend why Rubio, a senator from Florida, might lose Tuesday’s Republican presidential primary to Donald Trump.

Marco Rubio has been remarkably upbeat in the wake of primary losses. Now he's staking everything on Florida. (Peter Stevenson/The Washington Post)

“If people don’t want to listen to the truth, that’s their problem. This is a free country. But I would hope — God willing — he’ll help us to win,” she said as she choked back tears again.

Across Florida, longtime Rubio supporters are coming to grips with the possibility that the senator is probably on the verge of a humiliating defeat in the state’s GOP primary. Their young, telegenic favorite son who began as a city commissioner and was touted as the “Republican savior” continues to trail Trump in polls as the businessman has taunted him for weeks.

Campaigning statewide over the weekend, Rubio looked exhausted. He nearly lost his composure talking to reporters about violence at recent Trump rallies. He rushed through crowds at restaurants and retail shops, shaking hands, kissing elderly women, tilting his head and furrowing his brow to convey his appreciation. A funereal mood set in, similar to what cloaked the campaign of former Florida governor Jeb Bush in its waning days.

In Largo, his voice cracked as he acknowledged that “it’s getting harder every day” to fathom supporting Trump as the Republican nominee. Video of the moment quickly went viral, because it caught a rare flash of emotion from the usually scripted Rubio.

[Given violence, Rubio raises doubts that he can support Trump as the GOP nominee]

“I entered this campaign for president understanding that I wouldn’t be a front-runner,” he told about 300 supporters. “Told by many that had been in politics for a long time that it wasn’t my turn, that I needed to wait in line, that I was too impatient and in too much of a hurry. Yes, I’m in a hurry, and I’m in a hurry because I think America needs to be in a hurry.

“Now the time has come for this generation to do its part. And if we don’t get it right in 2016, I’m not sure what happens next,” Rubio added. “I’m not trying to be negative or cataclysmic or apocalyptic, I’m just telling you, I’m not sure what happens next.”

At Tiffany’s Family Restaurant in Palm Harbor, Rubio breezed through in 20 minutes amid customers dining on chocolate-chip pancakes. A group of elderly women quickly texted their selfies with the senator to family members.

“You’re a young man with a bright future,” an older man whispered to Rubio. “There’s always tomorrow.”

But Rubio interjected: “We got to get it this time, because America needs it now.”

Eleni Hittos, the restaurant owner’s mother, said that Rubio had never visited the restaurant before.

“He is a good man. Young man. And he’s energetic. And his background — his family coming from stupid Castro from Cuba there. We came from Albania, we escaped. So that’s why we believe in him,” she said.

“He’s going to win because I’m going to vote for him,” Hittos added. “Donald Trump, I won’t vote for him, because he’s a big baby.”

In New Port Richey, more than 200 people greeted Rubio at Ron’s Bar-B-Q. A young woman working at the Taco Bell next door persuaded her boss to let her slip out to see the senator. Residents living behind the restaurant in trailers offered parking spots in their yard for $10.

Bill and Katie Clum, retired school teachers, reluctantly acknowledged that their preferred candidate might lose on Tuesday.

“I’m concerned with how the media has trivialized some of the things he said,” Katie Clum said. “I think that they’re looking for ratings over issues and I think he got caught up in the backlash of that. That concerns me.”

Bill Clum said that Rubio’s chances were hurt because “Bush didn’t come out to support him. He worked with him and they were buddies, and as Floridians, we know that relationship. For Bush to not bury the hatchet and support him — that’s going to hurt.”

If Rubio loses, “I hope this doesn’t destroy him,” Katie Clum said.

As the senator boarded his bus, someone shouted, “Go, Marco! Keep fighting.”

“Please don’t allow Trump to win!” a man told him.

Watching the scene, a woman who declined to give her name said Rubio “is running against Satan. He really is.”

On Sunday, Rubio awoke to a new CBS News survey of Florida Republicans that placed him third behind Trump and Sen. Ted Cruz (Tex.). He returned to The Villages, a sprawling retirement community in central Florida where he campaigned to higher hopes in September. Later, he visited a campaign office in Orlando and greeted one of the more enthusiastic crowds he’d seen in recent days. Speaking with a bullhorn, he encouraged supporters to keep fighting. Boxes of Krispy Kreme donuts and empty soda cans were strewn across a table. Phone call instructions and scripts for volunteers were placed nearby.

To lift the team’s spirits, someone put up a sign in the office referring to Rubio’s long-shot Senate win in 2010. “He was the underdog here as well,” it read.

[Who should Obama meet with in Cuba? Marco Rubio has some ideas.]

Back in Miami, supporters are campaigning as though Rubio is running again for his first political job as a West Miami city commissioner nearly 20 years ago.

“We’re trying to address this like it would be a local election for us and trying to fan those flames to make sure people are coming out to vote,” said Esteban Bovo, a longtime Rubio friend and member of the Miami-Dade Board of Commissioners. “Nobody else has that kind of ground game in South Florida. Hopefully people turn out. That’s all we can do at this point.”

But former congressman Lincoln Díaz-Balart (R-Fla.), a Rubio backer, accused Rubio’s campaign of poorly organizing a rally last week in Hialeah, a Cuban American community. The event filled only a small portion of a football field, leading to embarrassing wide-shot images of the scene published on social media.

“I’m hopeful that it’s going to be close and that the polls are wrong,” Díaz-Balart said. “I’ve been surprised by this Trump thing, but around here, I don’t know a Trump activist.”

That means the former congressman doesn’t know Bertin Palomino. The 58-year-old Army veteran sat waving a Trump campaign sign in the parking lot because the businessman “cannot be bought by the GOP.”

Palomino has never voted for Rubio but said he used to drink coffee with the senator’s late father, Mario, at a spot near Tropical Park. During their conversations, Palomino recalled, the elder Rubio would say that “my son is going to grow up to be a great man.”

So did Mario Rubio raise a great man?

“I think he did,” Palomino said. “Marco is a really good, decent person. Politics is dirty. They say things about us, we say things about them. But when it’s over, it’s all forgotten.”

Sean Sullivan in Orlando contributed to this report.