Donald Trump's campaign manager has acknowledged that the Republican presidential nominee needs a "comeback" in the final weeks of the campaign.
Kellyann Conway said Mr Trump has pulled off comebacks several times before, but i t was a rare acknowledgement by the billionaire's campaign that he could ultimately fall short.
She was speaking to Fox News ahead of the third and final presidential debate and as a string of battleground state polls showed Hillary Clinton ahead.
Ms Conway said she does not understand why Mrs Clinton has not been able to "put him away" given her experience and her campaign's "endless amounts of money".
She said: "What is her problem, already?"
Meanwhile, Tim Kaine said he wants Mrs Clinton to "win big" so that no-one will believe Mr Trump's claims of a rigged election.
The Democratic vice presidential candidate was urging supporters in Ohio to run up the score against Mr Trump, who has made unsubstantiated claims that the election has been fixed in Mrs Clinton's favour.
Mr Kaine said that the bigger Mrs Clinton's margin of victory is, "the harder it is for him to whine and have anybody believe him".
He said Mr Trump's claims of election rigging are an insult to American democracy, adding: "It's shameful."
Mr Kaine said he hoped the moderator of Wednesday's presidential debate, Fox News host Chris Wallace, would challenge Mr Trump and not let him simply throw insults at Mrs Clinton.
No matter how persuasive the candidates are at Wednesday night's debate, it is already too late for either to win over millions of voters.
Advance voting by post or in person is now under way in more than 30 states and at least 2.1 million voters have already cast ballots.
More than 45 million people are expected to vote before Election Day on November 8.
In Nevada, site of the debate, absentee ballots were being posted on Wednesday.
Early balloting has so far shown promise for Mrs Clinton in battlegrounds North Carolina and Florida, while Mr Trump has generally held ground in Iowa and Ohio.
Early voting is traditionally favoured by Democrats and is a key part of the Clinton campaign's strategy.
Mr Trump is counting on a stronger performance on Election Day itself.