Former President Donald Trump raised doubts late Sunday about whether he would participate in the Sept. 10 debate against Vice President Kamala Harris on ABC.

Posting on Truth Social, the Republican presidential nominee suggested the network would be heavily biased against him. 

Mr. Trump cited a Sunday interview with Sen. Tom Cotton, Arkansas Republican and key Trump ally, on ABC and rattled off hypothetical questions about its journalists’ impartiality.

“And I ask, why would I do the Debate against Kamala Harris on that network? Will panelist Donna Brazil give the questions to the Marxist Candidate like she did for Crooked Hillary Clinton? Will Kamala’s best friend, who heads up ABC, do likewise. Where is Liddle’ George Slopadopolus hanging out now? Will he be involved,” Mr. Trump said, using a nickname for ABC News’ George Stephanopoulos and also referring to Democratic strategist Donna Brazile.

Mr. Trump and Ms. Harris agreed to the Sept. 10 debate on ABC after days of jockeying over dates and whether Mr. Trump should honor the agreements in place when President Biden was the presumptive Democratic nominee.

Mr. Trump, who likes to keep opponents and the media guessing, could be building suspense before the event, or he could be lowering expectations by suggesting the moderators will be on Ms. Harris’ side.

“They’ve got a lot of questions to answer!!!” Mr. Trump said. “Why did Harris turn down Fox, NBC, CBS, and even CNN? Stay tuned!!!”

Media reports, however, suggested the real problem has to do with stage rules.

Mr. Trump’s team would like the microphones to be muted when candidates aren’t speaking, while the Harris side would like to leave them on, according to multiple outlets.

“His handlers are insisting that his mic must be muted there,” Harris spokesman Ian Sams posted on X. “The American people deserve a back-and-forth debate where the two candidates can have real exchanges. Why is Trump so afraid of that?”

The Trump campaign says Ms. Harris is guilty of a bait and switch.

“We accepted the ABC debate under the exact same terms as the CNN debate [in June]. The Harris camp, after having already agreed to the CNN rules, asked for a seated debate, with notes, and opening statements. We said no changes to the agreed upon rules,” Jason Miller, a senior adviser for Mr. Trump, told Politico. “If Kamala Harris isn’t smart enough to repeat the messaging points her handlers want her to memorize, that’s their problem.”

• Tom Howell Jr. can be reached at thowell@washingtontimes.com.