JEB BUSH announced his long-awaited presidential campaign yesterday with a promise to beat the Democrats and take back the office once held by his father and brother.

But before Mr Bush can take on Hillary Clinton, he must first defeat his own political son. Standing between the former Florida governor and the prize Republican nomination is Marco Rubio, the senator who was once his protégé.

The 62-year-old Mr Bush helped guide Mr Rubio’s rise through Florida state politics and even presented him with a ceremonial sword when he became speaker of the state house of representatives.

Mr Rubio, 44, in turn deferred to the older man, praised his “bold leadership” as governor and sought Mr Bush’s help in his long-shot attempt to become a US senator in 2010.

Many did not expect Mr Rubio to run for the Republican nomination against his mentor. “We were very surprised,” said Dominic Calabro, the president of Florida Tax Watch, an independent government watchdog group. “People hoped they would be able to work it out, but that’s political competition.”

The two men formally became election rivals yesterday as Mr Bush declared his candidacy at a Miami college a few miles from where he and Mr Rubio both live.

“I will take nothing and no one for granted. I will run with heart. I will run to win,” Mr Bush said. His supporters waved signs with that read “Jeb!” but left out his surname. He lambasted the Democrats for a “no-suspense primary” in which Hillary Clinton’s victory looks all but certain and declared “it’s nobody’s turn” to be president. Having taken several veiled swipes at Mr Bush in his own Miami announcement speech in April, Mr Rubio yesterday welcomed him to the race.

“When I call Jeb Bush my friend, I mean he is someone I like, care for and respect,” he said.

The looming battle between the two men is more than just a drama between a former political student and master. While as many as 20 Republicans may end up trying to run for president, Mr Rubio and Mr Bush share a similar optimistic message and will be competing for the same voters.

Bush aides say privately that Mr Rubio is the biggest threat to their White House hopes, far more than Mrs Clinton. Both men are presenting themselves as candidates who can appeal beyond white voters and win over parts of America’s rapidly growing Latino population.

Mr Rubio talks on the campaign trail about how his Cuban parents arrived in Florida in pursuit of the American dream and switches effortlessly between English and Spanish.

Mr Bush describes how his life truly began when he met his wife Columba as a 17-year-old studying in Guanajuato, Mexico. He, too, speaks fluent Spanish although his is twanged with the accent of his native Texas. “When Hispanics hear an Anglo speaking Spanish, even with an accent, we do appreciate it,” said Nelson Diaz, chairman of the MiamiDade County Republicans.

There are few Hispanics in Iowa and New Hampshire, states holding early primaries, but are expected to make up around 20 per cent of the electorate in Florida. “Florida is one of the few states where enough Hispanics vote in a Republican primary to be a significant force,” said Larry Sabato, a politics professor at the University of Virginia.