There is Never a Single Reason

But Kamala Harris' decision to make Elizabeth Cheney's endorsement of her central to the campaign was an own goal of epic proportions.

It was pandering to a section of the electorate, never-Trumpers, who were already going to vote Harris and whose numbers were vanishingly small.

Additionally, it served to demoralize potential supporters.

Kamala Harris made her first campaign appearance with Liz Cheney in Ripon, Wisconsin, the birthplace of the Republican Party, one month and two days before the 2024 election. The point of the visit was to signal to conservatives that they could split with Donald Trump’s Republican Party over their concerns about the former president’s election denialism, authoritarian rhetoric, and embrace of global strongmen. Republicans could, Cheney argued, cast a “Country Over Party” vote for the Democratic presidential nominee—just like the former chair of the House Republican Conference, who broke with Trump over his refusal to accept the results of the 2020 election, planned to do.

The media loved the story. Lavish attention was paid to the event. Cable channels went live. Ponderous essays were written in the great newspapers of the nation about the prospect that Harris would attract enough Republican votes to upend Trump’s bid for a second term.

Unfortunately, while many Democratic tacticians were enthusiastic about Cheney’s jumping on board as a Harris backer, Republican voters couldn’t have cared less. The Cheney strategy was an abject failure that added few if any votes to the Democratic total, alienated voters who have no taste for the former GOP representative’s neocon extremism, and stole precious time from an agonizingly short campaign schedule.

I'm sure that Harris' advisers thought that this was a good idea, but these advisors are all a product of the Democratic Party establishment (There is no Democratic Party establishment) political consultancy community, and they thought that it was a good idea because running on nothing makes said political consultants money.