MIAMI — The tattered American flag that hung inside Marco Rubio's office when he was Florida House speaker was a patriotic statement, a nod to his immigrant family's success story — and a sign of his close relationship with the man who loaned him the 1775 antique, an auto magnate named Norman Braman.

Eight years later, the flag is back in Braman's Miami conference room, because U.S. Senate rules won't let Rubio display a constituent's collectible in Congress. Its next stop, Braman hopes, could be the White House.

Braman, the billionaire philanthropist, history buff and civic activist who four years ago orchestrated the ouster of a Miami-Dade County mayor, plans to bet big on Rubio as the Republican senator prepares for a 2016 presidential run. Braman won't say how much he could donate to Rubio's likely campaign, but the number is said to be around $10 million.

This eye-popping investment could signal conservative groups, including the Club for Growth and uncommitted donors such as Las Vegas casino billionaire Sheldon Adelson, to keep open minds — and wallets — toward Rubio. Their support could give him the financial prowess to stay in the race for the long haul if, as expected, Rubio declares his candidacy next month.

"He knows the odds, and I know the odds, but when he comes in contact with individuals, he's impressive," Braman said in a recent interview at his office on the second floor of his Biscayne Boulevard car dealership. "I think he's catching fire already."

Rubio declined to be interviewed through spokeswoman Brooke Sammon, who said the senator has "known Braman for years, and he values their friendship and appreciates his support." Braman, through his charity foundation, also employs Rubio's wife, Jeanette.

Despite their age difference — Braman is 82 and Rubio is 43 — the two friends speak occasionally, either on the phone or by text messages, Braman said. He insisted he doesn't weigh in on policy matters, though Braman, who is Jewish, cares deeply about Israel, and Rubio, who is Catholic, has emerged as an outspoken Israel hawk.

Braman and other wealthy benefactors have had an outsize influence on campaigns since a 2010 U.S. Supreme Court decision allowed unlimited contributions to political action committees known as Super PACs. The committees have become candidates' primary fundraising vehicles, though they're prohibited from coordinating with politicians once they formalize their candidacies.

"Norman Braman is a plus, no matter what, but in the age of the Super PAC, if a billionaire befriends you and really wants to assist your presidential aspirations, it can really go a long way," said Brian Ballard, a Florida Republican lobbyist and fundraiser who is backing the all-but-declared candidacy of former Gov. Jeb Bush. "Usually these folks travel in circles where they have a great deal of influence over their friends and people who do business with them."

In 2012, two Republicans bankrolled chiefly by billionaires — Rick Santorum by Foster Friess, and Newt Gingrich by Adelson — hung in the primary race largely thanks to their moneyed financiers.

A single affluent donor may not be "determinative," Ballard added, "but I think it's exceptionally helpful." Bush and other GOP hopefuls have also lined up other billionaires' support.

Roots of friendship

Rubio's relationship with Braman dates to his first years in the state Legislature. "He was a young man, but he had ideas," Braman said. "He was never conventional."

Braman seemed less impressed by then-Gov. Bush, who in 2004 vetoed $2 million from the state budget for the Braman Family Breast Cancer Institute at the University of Miami. Braman said Bush never explained his decision to him.

"I wasn't too happy with that veto," he said.

In Rubio, Braman found a kindred spirit who believed in small government and was the son of immigrants. Braman's mother was a seamstress from Romania and his father a barber from Poland; Rubio's mother was a maid and father a bartender, both from Cuba.

Braman has a deep admiration of immigrants. He recounted the long hours worked by two Central American women, mothers of college students, who cut his hair and do his nails at the DoubleTree Grand Hotel Biscayne Bay salon.

"Unlike the people in politics who were born on third base and think that they hit a triple, Sen. Rubio comes from a background similar to mine," Braman said, taking a swipe at Bush with a line the late Texas Gov. Ann Richards deployed against Bush's father, George H.W. Bush, at the 1988 Democratic National Convention.

Campaign-contribution limits kept Braman from donating significant amounts to Rubio while he was in the state House of Representatives. Records show Braman and his wife, Irma, gave him $5,000 between 2004 and 2006.

The Bramans and their companies also contributed nearly $563,000 to the Republican Party of Florida from 2005 to 2008. Rubio's spending came under scrutiny during his 2010 Senate race, when the Times/Herald found he rang up about $100,000 on a RPOF-issued credit card. The charges ranged from meals and travel to a family minivan repair. Rubio has said that most of the expenses were for party business and that he paid back any personal charges.

Toward the end of Rubio's term, Braman conducted a poll pitting Rubio as a possible challenger to Miami-Dade Mayor Carlos Alvarez, who had pushed for public financing that Braman opposed for a new Florida Marlins ballpark. Rubio wasn't interested. Braman would have to wait until 2011 to campaign against Alvarez in what was at the time the biggest recall of a local politician in U.S. history.

Rubio's Senate run

Rubio set his sights on the U.S. Senate, in an unlikely primary bid against then-Gov. Charlie Crist. Among the few early Rubio believers was Braman, who had contributed to Crist's campaign for governor and said Crist invited him to his 2008 wedding.

"But I told him, 'If Marco decides to run, I'll support him,' " Braman said. "At the time, there weren't too many of us."

Rubio was "lonely" at the time, Braman added — in some ways, as he is now, with affluent Florida donors pledging loyalty to Bush.

"I just remind everybody that those were the same people that were giving Gov. Crist money as well," said Braman, who along with his wife ended up giving $9,600 to Rubio's Senate campaign and more than $60,000 to the National Republican Senatorial Committee, according to the Center for Responsive Politics.

Win or lose, the Rubios and Bramans organized a trip to Israel after the Senate race. Sen.-elect Rubio turned down Braman's offer to fly on Braman's private jet, saying Senate rules would prohibit him from doing so if he were already sworn in. Rubio and his wife flew coach.

In 2013, the Braman Family Foundation hired Jeanette Rubio to review charity grant applications, according to the foundation's tax return. She works part-time for Braman's daughter Debra, the foundation's executive director, and also helps the family with its personal charity-giving, Braman said.

Braman predicts Rubio will face criticism as a potential 2016 presidential candidate for having served only one Senate term, a frequent attack leveled against President Barack Obama — and for sponsoring immigration-reform legislation that Braman supports but that riled the conservative GOP base.

Rubio is not enamored by the Senate, Braman said. "I know he's frustrated with the fact that the issues are not debated in Washington. He really, genuinely feels that."

Al Cardenas, a former Florida GOP and American Conservative Union chairman and longtime Bush adviser, said Braman's backing will probably be a key factor in Rubio's ultimate decision.

"He's a mentor to Marco in many ways," Cardenas said of Braman. "And whether political candidates admit it to the press or not, they just know how challenging it is to gather the resources to last through even the first primary.

"These races are beginning a year before Iowa, and they're getting very, very expensive."

Contact Patricia Mazzei at pmazzei@miamiherald.com.