MIAMI—In the early days of Marco Rubio’s campaign for U.S. Senate, he spoke at one of the first Tea Party rallies in the state of Florida.

As Rubio began to speak about not wanting to lose his country to socialism, lightning reportedly began to flash. It was to be either an omen of the betrayal his Tea Party supporters would later feel, or a foreshadowing of the powerful potential this young Cuban American had for higher office.

It had taken a month for his hometown newspaper, the Miami Herald, to notice that the 38-year-old Miami lawyer, once a leader in the state House, had formally joined the race. He didn’t even hold a launch event when he registered as a candidate for U.S. Senate in early 2009.

“It was lonely out there. He was living off the land,” an early supporter said. “If he had held a launch event for his U.S. Senate campaign, you could have held it in a phone booth.”

It was the excitement of the Florida Tea Party movement, which exploded into the public consciousness in the spring and summer of 2009, that ultimately transformed Rubio into a serious contender.

“Across the board in 2010, the Tea Party played a huge role. They got people out to vote, they were active, they were knocking on doors, making phone calls. There were little spots during the campaign where you just felt the momentum,” said Anthony Bustamante, Rubio’s former statewide field director and one of the first half-dozen staffers to join the Senate campaign.

But don’t count on many of those original Florida Tea Party supporters to be in the crowd Monday evening when Rubio is expected launch his bid for the White House with dramatic fanfare at Miami’s Freedom Tower, converted in the 1990s as a monument to Cuban refugees.

Six years after the movement’s initial rallies, marches, and demonstrations, Tea Party activists feel let down and betrayed by their native son.

“I’m through with him. He will never get my vote. ‘Disappointed’ would mean that he has an opportunity to restore his credibility, and there is no opportunity for that,” said KrisAnne Hall, an attorney and Tea Party activist from north-central Florida. “The overwhelming perception is that Marco Rubio is not a Tea Party candidate.”

Some Florida Tea Party supporters still wax nostalgic about the early, hopeful days of the Rubio Senate campaign.

“When he was first running for Senate, I was a big fan…He walked the neighborhood both inside and outside his district, knocked on doors and asked what people’s needs were, what their issues were. I was so impressed with that,” said Lisa Becker, who helped run A Sisterhood of Mommy Patriots, a Tea Party group geared toward mothers.

“Then,” Becker continued, “he got into office.”

“Once he got into Washington, he had his sights set early on higher office,” said Jason Hoyt, a Tea Party organizer from central Florida. “He surrounded himself with people who were going to help him navigate Washington to get there, and in that process he disconnected from his base.”

Becker still acknowledges Rubio’s charisma and oratorical abilities. But now she thinks she might have been played.

“Now I wonder if he was ever listening or it was just a ploy to get votes…He says all the right things to the audience he needs, and we in Florida are no longer his audience. His new audience is national voters who might elect him president,” she said.

“We were hungry for leadership on our principles and values, but it didn’t come from Marco,” Hoyt added. “I thought it would.”

Many Tea Partiers point to Rubio’s work in the Senate as part of the so-called Gang of Eight, who tried to come to a bipartisan consensus on comprehensive immigration reform. It ultimately failed, but many on the right will not forgive what they disdain as the senator’s support for “amnesty.”

At the Conservative Political Action Conference this year, Rubio tried to distance himself from his work on immigration, saying he had learned his lesson—that broad-based reform was only possible after complete border security.

Some libertarian-leaning Tea Party activists also point to foreign policy and national security as issues on which he let them down. Hall, the attorney from north-central Florida, listed off the offenses: Rubio’s support for indefinite detention, support for arming the Syrian rebels, support for the war against ISIS without explicit congressional approval, and support for the NSA.

“If he had been listening when he was knocking on those doors, he would have found out what matters. Being in perpetual war matters to families,” Becker said.

Bustamante, Rubio’s former statewide field director, plays down any discontentment Florida Tea Party activists feel about the Florida Republican senator.

“I don’t think there’s a rift. The Tea Party embraced Marco. I think they still hold them up as one of their own,” he said.

Tom Gaitens, who knew Rubio in the state House and formerly worked for the conservative group FreedomWorks, said he had forgiven Rubio for the sin of working with Democrats on comprehensive immigration reform.

“The only perfect guy I ever met was Jesus Christ, in my heart. What I care about is that they stand up and show courage, and I think Marco has done that every step of the way,” Gaitens said.

And Rubio is still an insurgent. He is far from the front-runner in the large Republican presidential field.

It’s a position where he has thrived: Bustamante recalled the early “startup” days of the Rubio Senate campaign, where they drove 10 hours round trip to Jacksonville just to make $900.

Rubio is not running a startup anymore. He’s running a full-fledged business that hopes to raise millions to elevate him to the White House.

This time, though, he’ll do it without the support of many of the grassroots activists who propelled him to the Senate hoping for a Tea Party champion.