The campaigns of Vice President Kamala Harris and former President Donald Trump are arguing in advance of their high-stakes Sept. 10 debate over whether microphones should be muted except for the candidate whose turn it is to speak.

While it’s common for campaigns to quibble beforehand over debate mechanics, Harris and Trump are under pressure to deliver a strong performance next month in Philadelphia. The first debate during this campaign led to President Joe Biden’s departure from the race.

Trump raised the possibility Sunday night that he might not show up on ABC, posting on his Truth Social network that he had watched the network’s Sunday show with a “so-called Panel of Trump Haters” and posited “why would I do the Debate against Kamala Harris on that network?” and urging followers to “Stay tuned!!”

The dispute centers on the muting of microphones when a candidate isn’t speaking, a condition Biden and Trump accepted for their June debate hosted by CNN. Both sides are accusing the other of gaming the system to protect their candidate.

Biden’s campaign team made microphone muting a condition of its decision to accept any debates this year; some aides now regret the decision, saying voters were shielded from hearing Trump’s outbursts during the debate. That move likely would not have helped the Democrat’s disastrous performance.

The Harris campaign now wants microphones to be live all the time, according to Harris spokesman Brian Fallon, who issued a statement needling Trump.

“Trump’s handlers prefer the muted microphone because they don’t think their candidate can act presidential for 90 minutes on his own,” Fallon said. Harris “is ready to deal with Trump’s constant lies and interruptions in real time. Trump should stop hiding behind the mute button.”

Trump spokesman Jason Miller retorted that the Republican nominee had “accepted the ABC debate under the exact same terms as the CNN debate.”

“I’d rather have it probably on,” Trump said Monday during a stop in the Washington area, when asked if he wanted microphones muted.

Asked how he was preparing for the debate, Trump responded, “I’m not. ... I think my whole life I’ve been preparing for a debate.”

Complicating the negotiations this year is that debates are being orchestrated on an ad hoc basis by host networks, as opposed to the bipartisan Commission on Presidential Debates, through which debate rules were negotiated privately.