Democratic presidential hopeful former US Representative for Texas' 16th congressional district Beto O'Rourke gestures as he speaks during the first Democratic primary debate of the 2020 presidential campaign season hosted by NBC News at the Adrienne Arsht Center for the Performing Arts in Miami, Florida, June 26, 2019.

Former Texas Rep. Beto O'Rourke's top donors and bundlers are looking for him to improve in the next debate after they spoke with him on a conference call Thursday to discuss his poorly reviewed Wednesday night performance.

In a discussion that was planned the day before the debate, the former Texas lawmaker's lead fundraiser, Louis Susman, organized a call with O'Rourke himself and other financial supporters to speak at length about how he fared throughout the showdown with nine other 2020 contenders, according to people with direct knowledge of the matter.

Susman was a top bundler for former President Barack Obama's first presidential campaign in 2008 and was later nominated to be the U.S. ambassador to the U.K. He helped raise at least $500,000 for Obama at that time, according to the nonpartisan Center for Responsive Politics.

While several O'Rourke donors and grassroots organizers on the call expressed their belief that he had a strong performance during the debate, contrary to the broader consensus, there were some on his team who gave their takes on how he could improve on his performance in Miami, these people added.

"My big takeaway is Beto is perceived as a much larger threat than I even thought this early in the race," after the debate, one of the donors on the call told CNBC on the condition of anonymity because the meeting was deemed private. Still, the donor also noted "the platform last night was clearly out of his comfort zone."

The financier added that O'Rourke "will be aware of what he needs to do to prepare for the next debate, and fortunately the needed improvements are purely stylistic."

Longtime Democratic donor Robert Wolf, also an O'Rourke supporter, told CNBC that he believes Sens. Elizabeth Warren, Cory Booker and former HUD Secretary Julian Castro were the winners of Wednesday's debate. Wolf declined to give his take on O'Rourke's performance.