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, both 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.