WASHINGTON — Liz Cheney, one of former President Donald Trump’s fiercest Republican antagonists, will join Vice President Kamala Harris at a Democratic campaign event Thursday in Wisconsin aimed at reaching out to moderate voters and rattling the former president.

Cheney was the top Republican on the House committee that investigated the Jan. 6, 2021, insurrection, earning Trump’s disdain and effectively exiling herself from her own party.

She lost her Wyoming seat to a Trump-endorsed candidate two years ago, and she endorsed Harris, the Democratic nominee, last month. The women will appear together at a college in Ripon, home to a white schoolhouse where a series of meetings in 1854 to oppose slavery’s expansion led to the birth of the Republican Party.

Harris is opening a two-day trip to Wisconsin and Michigan, and Trump will be in Michigan on Thursday as the two candidates grapple for wins in the “blue wall” battleground states, which include Pennsylvania.

President Joe Biden said Thursday that he wasn’t concerned about a Trump-Harris race coming down to the wire because “it always gets this close.”

“She’s gonna do fine,” Biden said to reporters on the South Lawn of the White House on his way to visit storm-ravaged Georgia and Florida.

It’s uncommon, to say the least, for a candidate to give a nod to the origins of the opposing party in the closing weeks of a presidential campaign. Not only that, the Cheney name was once anathema to Democrats who deplored Dick Cheney, Liz’s father, for his role as vice president to President George W. Bush.

During the 2020 campaign, Liz Cheney criticized Harris as “a radical liberal” who “wants to re-create America in the image of what’s happening on the streets of Portland & Seattle,” a reference to unrest that took place in those cities after the police murder of George Floyd.

But Jan. 6 was a turning point for Cheney and her family.

Both Cheneys are backing Harris, part of a cadre of current and ex-GOP officials who oppose Trump.