A planned meeting between Joe Biden and Senate Democrats set for Monday was ultimately canceled, as several Democrats continue to voice their concerns about Biden’s cognitive abilities and the possibility that he could lose the November election to Trump.

According to Axios, the attempted meeting was being arranged by Senator Mark Warner (D-Va.), who has been talking privately to his Democratic colleagues about his concerns over Biden’s capability of remaining in the presidency or winning another four years in the fall. Part of the reason for the meeting’s cancellation was the leak of detailed information about the meeting itself, which eliminated the privacy of the planned discussion.

Congress returns to session on Monday, and the regularly-scheduled Democratic caucus meeting will still take place on Tuesday.

The attempted meeting is the latest example of internal Democratic concerns about Biden’s mental state following a disastrous performance in the first presidential debate against Donald Trump in late June. Noted for his awkward pausing, stammering, and incoherent answers, Biden’s performance has been deemed the worst in the history of televised presidential debates.

Speculation has since abounded that Biden could be forced out as the party’s nominee, and even the presidency itself via an invocation of the 25th Amendment by Congress. The Democratic National Convention, where the formal nomination of a presidential and vice presidential candidate will take place, is scheduled for August 19th to August 22nd.

Since the debate, nine current members of the House of Representatives have publicly called on Biden to withdraw from the race, with the first being Congressman Lloyd Doggett (D-Texas) and the most recent being Congressman Jerry Nadler (D-N.Y.). But other well-known Democrats, including Senate Majority Leader Chuck Schumer (D-N.Y.) and former presidents Bill Clinton and Barack Obama, have stood behind Biden as the nominee.