The financial woes of President Donald Trump's campaign have forced him to scale back TV advertising in Florida, Iowa and Nevada just as Joe Biden pours huge sums into a burst of spots across battleground states.
The former vice president has bought $US54.1 million ($A76.6 million) in TV ads for the eight days before the election, more than double Trump's $US26.9 million, according to ad tracker Advertising Analytics.
The playing field for TV ads will tilt further toward the Democratic nominee on Wednesday as former New York mayor Michael Bloomberg starts spending $US15 million on Texas and Ohio spots to attack Trump's handling of the COVID-19 pandemic.
In 2016, Trump won Texas by 9 percentage points and Ohio by 8 but recent polls show the race now virtually tied in both.
Bloomberg, a billionaire who is also spending $US100 million in Florida on TV ads and other efforts to defeat Trump, conducted polling over the weekend that convinced him to big play in Texas and Ohio.
"I would argue both of those states right now are toss-ups in ways that I think will surprise people, win or lose, the day after the election when their results are in," said Bloomberg adviser Kevin Sheekey.
The new Bloomberg spending was first reported by The New York Times. He spent a billion dollars of his fortune on his own failed primary bid for the Democratic nomination.
It's unclear whether TV ads can sway many voters in the closing days of the race. Nearly 70 million Americans have already cast ballots, according to the nonpartisan US Elections Project.
Biden's ad spending spans the entire map of election battlegrounds.
For the campaign's final week, he has increased his TV ad buys in Pennsylvania, Florida, Arizona, Michigan, North Carolina, Wisconsin, Georgia, Iowa, Ohio, Nevada, Minnesota, Texas and New Hampshire.
In every state, he is outspending Trump.
Trump, who has lagged far behind Biden in fundraising, is allocating his money to a shrinking set of states and he's relying heavily on the Republican National Committee to buttress his spending in the final stretch.
Trump's triage - he has yanked tens of millions of dollars in advertising that he'd initially booked for the fall campaign - is revealing of how his campaign sees the president's most promising path to victory in the state-by-state contest for an Electoral College majority.
Trump has increased his TV ad spending this week in Pennsylvania, Wisconsin and Michigan, suggesting he's banking on maximizing support among white working-class voters in those northern industrial states, just as he did four years ago.
His narrow wins in them enabled him to capture the presidency despite losing to Hillary Clinton in the popular vote.
Trump also sharply increased his spending this week in Minnesota, which Clinton won by just 1.5 percentage points.
Campaigning in Tuesday in Michigan, Trump predicted he would win Minnesota this time in part because of ill will toward Democratic Representative Ilhan Omar, one of the first two Muslim women in Congress.
He also said anger over protests in the city after the police killing of George Floyd would bring him voters.