Mid-morning Tuesday on Florida primary day, Artemio Muñiz was in a truck with Marco Rubio team members heading to a heavily contested Miami precinct where he expected to find Donald Trump and Rubio supporters.
"Florida is the line for the future of the GOP. That's why I'm here," said Muñiz, who runs the Federation of Hispanic Republicans, part of the Texas Republican Party.
"It feels like a proxy war for the soul of the conservative movement, of the Republican party," he said.
The polls have painted a grim picture for Rubio's presidential candidacy, showing Trump ahead in Rubio's home state of Florida that offers the top finisher in the GOP all 99 of its delegates.
But a number of Latinos from around the country, many who first backed Jeb Bush, have poured their hopes and resources into Rubio as the anti-Trump candidate they could back in a general election.
Muñiz said he traveled to Miami to watch the primary unfold, but has thrown himself in the mix in a last stand effort to keep Rubio's campaign alive.
Tuesday morning he was traveling with campaign workers delivering sustenance -- snacks and water -- to precinct captains, helping put up signs and urging voters to cast their ballots for Rubio. He said he's been impressed with the ground game and the Cuban community support that Rubio is getting.
"A number of Latinos from around the country, many who first backed Jeb Bush, have poured their hopes and resources into Rubio."
"In Texas ... we are still trying to figure out who we are. If Florida goes for Rubio, it will be the Cuban community that saved the GOP," Muñiz said.
On Monday, Rubio emphasized his Cuban-American roots to supporters who rallied at the City of West Miami basketball court. Using a bullhorn and delivering half of his speech in English and the other half in Spanish, Rubio emphasized that the community needed to turn out.
Rubio told the crowd how he'd change the White House if elected, including bringing to it a "caja china," a pork roaster used by Cubans and getting the White House kitchen to make pastelitos de guayaba, the well-known Cuban pastries with guava.
Rubio's campaign is hoping turnout from the Cuban community offsets Trump support.
But amid the hope, there was some nail-biting going on among Rubio supporters.
Alfonso Aguilar, spokesman for a group of GOP Latinos who have publicly condemned Trump and Ted Cruz for their views and rhetoric on immigration, said if Rubio won Florida it would be a "political miracle."
"It would be a major upset, certainly it would be a game changer because no one is expecting it," Aguilar said. "What are the chances of that happening? I'm not sure."
But he pointed to Bernie Sanders' win in Michigan, which defied the polls.
"The only thing I know is I don't want Trump to win and I don't want Trump to be president," Aguilar said.
Peter Vivaldi, an Orlando-based consultant to the National Latino Evangelical Coalition, said he was "reliving 2010," the year of Rubio's U.S. Senate victory. Rubio started out behind, but ended up winning with an overwhelming margin after the once-leading Republican candidate, Charlie Crist, dropped out to run as an independent.
Vivaldi was joined in a radio broadcast of I Need to Know Radio in Orlando, also broadcast on Periscope, to urge Latinos to vote and to promote Rubio.
"I believe he's the only candidate that's gone out there to connect with Hispanic voters. I've seen others come in a week before and try to open 10 offices," Vivaldi said referring to, but not mentioning Ted Cruz, who recently opened several offices in Florida.
Muñiz said there is more riding on the primary than Rubio's campaign. The outcome would determine "what the GOP is going to be like," he said. "If it's not Rubio, the GOP loses the general."
This story includes material reporting from NBC's Alex Jaffe.