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Donald Trump pulled the trigger on a on Tuesday, setting the stage for a bruising Republican nomination battle after a showing by his hand-picked candidates weakened his grip on the party.

"America's comeback starts right now," the former president told hundreds of supporters gathered in an ornate American flag-draped ballroom at his palatial in Florida.

"In order to make America great and glorious again, I am tonight announcing for president of the United States," said the 76-year-old, who filed his official 2024 paperwork with the US election authority moments earlier.

Trump's unusually early entry into the White House race is being seen in Washington as an attempt to get the jump on other Republicans seeking to be the party flag-bearer -- and to stave off .

Republicans are licking their wounds after disappointing midterms, widely blamed on the underperformance of Trump-anointed candidates, and some are openly asking whether Trump -- with his divisive brand of politics and mess of legal woes -- is the right person to carry the party colors next time around.

Several possible 2024 primary rivals are circling, chief among them the governor of Florida Ron DeSantis, who bucked the tide and won a resounding reelection victory on November 8.

Trump, who lost the 2020 election to Democrat Joe Biden after being impeached twice by the House of Representatives, launches his new bid with several potential handicaps.

He is the target of multiple investigations into his conduct before, during and after his first term as president -- which could ultimately result in his disqualification.

These include allegations of fraud by his family business, his role in last year's attack on the US Capitol, his attempt to overturn the 2020 election, and his stashing of classified documents at Mar-a-Lago.

With Trump now a declared candidate, Biden's attorney general, Merrick Garland, may be forced to name a special counsel to pursue the various investigations into the former president launched by the Department of Justice.

Popular support

In addition, the powerful media empire of Rupert Murdoch has appeared to turn its back on Trump, labelling him after the midterms as a "loser" who shows "increasingly poor judgement."

Trump also remains banned by Facebook and Twitter, which was instrumental in his stunning political rise.

In a combative speech, Trump attacked Biden over inflation and crime and lauded his own accomplishments as president, including toppling the Islamic State and building a border wall with Mexico.

"Under our leadership, we were a great and glorious nation. But now we are a nation in decline," he said.

"In two years the Biden administration has destroyed the US economy," he said. "With a victory we will again build the greatest economy ever.

"The blood-soaked streets of our once great cities are cesspools of violent crimes," he said, vowing to "restore and secure America's borders."

The 79-year-old Biden has said his intention is to seek a second term -- but he will make a final decision early next year.

"I will ensure that Joe Biden does not receive four more years," Trump vowed, while the US leader greeted Trump's announcement with a tweet saying: "Donald Trump failed America."

Trump had made denial of the 2020 election results a key litmus test for midterm candidates seeking his endorsement -- but a string of defeats by loyal allies sapped his momentum in preparing a new White House bid.

Having failed to wrest control of the Senate, Republicans appeared poised to take over the House, but with a razor-thin majority.

Despite his lackluster election performance, the real estate tycoon retains an undeniable popularity with the millions of grassroots supporters who have flocked to his "Make America Great Again" banner.

And though abandoned by several top Republican donors, he has amassed a campaign war chest of well over $100 million.

2024 challengers

For the moment, the hard-right DeSantis looks like the leading challenger to Trump in a Republican field that may include former vice president Mike Pence, Texas Senator Ted Cruz, Virginia Governor Glenn Youngkin, former secretary of state Mike Pompeo and ex-South Carolina governor Nikki Haley.

The 44-year-old DeSantis, dubbed "Ron DeSanctimonious" by Trump, had a ready reply Tuesday when asked about the former president's attacks on him, urging "people to go check out the scoreboard from last Tuesday night."

Without naming Trump, he also suggested a Republican ticket headed by the former president would have trouble attracting independent voters "even with Biden in the White House and the failures that we're seeing."

By throwing his hat in the ring, Trump is seeking to become just the second American president to serve non-consecutive terms -- Grover Cleveland was elected in 1884, lost in 1888, and won again in 1892.