Cheney, on the Sidelines as Harris Courts Her Endorsement, Plans to Weigh In Soon

In reality, Ms. Cheney has been virtually silent since Ms. Harris became the Democratic nominee last month, except to say that Mr. Biden’s decision to step aside was “courageous.” As the campaign has started a “Republicans for Harris” organizing program with a full-time national engagement director and a seven-figure ad buy targeting anti-Trump Republicans and swing voters, she has been conspicuously absent from its rollout of dozens of new G.O.P. endorsements.

That is not expected to be the case for much longer. Ms. Cheney, who continues to describe Mr. Trump as “unstable” and “depraved,” has decided that September will be her moment to weigh in, according to three people familiar with her thinking, when early voting has begun and her voice will not be lost in a sea of back-to-back convention speeches.

Her objection to speaking in Chicago was almost entirely about timing, people familiar with her thinking said. It was a political calculation — which some of her allies disagreed with — about when she could maximize her impact on the outcome of the race.

But the vice president fanned speculation about whether an alliance could be in the offing during a CNN interview on Thursday night in which she said that if elected, she would name a Republican to her cabinet. Ms. Cheney’s name immediately began trending on social media, as Democrats and anti-Trump Republicans fantasized about the prospect of their unexpected hero serving in a Harris administration.

Democrats and other Republicans committed to defeating Mr. Trump view Ms. Cheney as a unique figure who can help with a critical slice of the electorate that the campaign is betting big on. Campaign officials note that almost one million voters in swing states cast ballots against Mr. Trump in the Republican primary, and could be ripe for the taking for Ms. Harris.