Vice President Kamala Harris is shifting her campaign strategy to win over more men and Republicans, and sharpening her attacks on Donald Trump as Democratic anxieties rise over polls showing her rival making strong gains.

The Democratic nominee is in a statistical dead heat in crucial states with Trump, the Republican former president, according to public and internal campaign polls cited by Democratic sources, sparking a round of finger-pointing and second-guessing from some corners.

It is a frustrating moment for a whirlwind campaign that opened with a huge jump in enthusiasm and cash when she replaced President Joe Biden in July, put on a robust Democratic convention and was widely hailed as the winner of her only debate with Trump.

"This was always going to be a tight race...That doesn’t mean we’re not losing sleep over it," said a senior Democratic campaign aide, reflecting what interviews with donors, aides and advisers show is the mood at the White House and the Wilmington, Delaware-based campaign headquarters.