WITH just 15 days to go before the US election, Donald Trump is campaigning in the must-win state of Florida as Hillary Clinton tries to slam the door on her Republican opponent in New Hampshire.

At the same time, Democrats are continuing to receive help from President Barack Obama, whose high job approval numbers have made him a political force in the sprint to November 8.

The president lashed out at Trump and praised Clinton as he campaigned in Nevada, a competitive state in the race for the White House and for the US senate election.

President Obama told Nevadans they have a winning hand in Clinton and Senate candidate Catherine Cortez Masto, who is locked in a tight race to fill the seat being vacated by the retirement of the Democratic senator Harry Reid.

Democrats need to retain the Nevada senate and pick up four new seats elsewhere to claim the Senate majority if Clinton wins.

Many Republicans fear that Trump’s struggles could drag down his party’s chances in competitive house and senate elections across the nation.

The current US president was unsparing in his criticism of Trump, describing the billionaire businessman as unfit for the White House.

Obama also railed against Republicans and conservative media outlets for promoting “all kinds of crazy stuff” about him and his party’s leaders.

He cited as an example questions from Trump and others about whether he was born in the US.

“Is it any wonder that they ended up nominating somebody like Donald Trump?” Obama said.

Trump, meanwhile, lashed out at his Democratic opponent on Twitter, claiming that “Crooked Hillary” wants the US to accept “as many Syrians as possible” from the war-torn region.

Clinton has said Obama’s plan to admit 10,000 Syrian refugees this fiscal year is a good start, but that the nation “needs to do more”.

Trump was campaigning in Florida, a state his advisers concede he must win to have any chance of becoming president.

Clinton’s running mate, Virginia governor Tim Kaine, was set to make two campaign stops in Florida yesterday. Clinton plans to visit the state today.

Her current focus is New Hampshire, a state that offers just four electoral votes compared to Florida’s 29, but marks a key piece to Trump’s increasingly narrow path to the 270 electoral votes needed to win the presidency.

The Trump campaign, which has faced a barrage of criticism and controversy, meanwhile, acknowledged its challenge in a new fundraising email, conceding that victories in marginal states like Florida, Ohio, Iowa, Nevada and North Carolina would not be enough to reach the 270 mark.

Republican campaign managers, however, still believe victory is in sight

“Polls show us close in New Hampshire, Colorado, and Pennsylvania.

“Winning just any one of those states would lead us to victory,” the campaign wrote.

Early voting by mail has been under way for weeks. Nearly

1.2 million voters in Florida have already mailed in ballots. The state has nearly 13 million registered voters.