As the GOP presidential candidates prepare for Wednesday’s primary debate on CNBC, a new poll by CBS and The New York Times indicates that onetime juggernaut Donald Trump continues to see his support erode.

Multichannel News reports that in the early primary state of Iowa, the poll shows retired neurosurgeon Ben Carson ahead of Trump, with 26% of Republican primary voters in Iowa supporting Carson to 22% for Trump — still within the poll’s margin of error.

Marco Rubio is in third place with 8%, followed by Jeb Bush and Carly Fiorina, both with 7%.

The poll, conducted Oct. 21-25, also shows that 7 out of 10 GOP voters have not yet made up their minds, which could ratchet up the stakes in Wednesday’s debate.

The Washington Examiner notes that the moderators for the debate include at least one person who could be problematic for Trump — John Harwood, who has been described as a “Trump skeptic.”

Trump “will once again face a member of the news media who will act as a moderator, but who long ago wrote off his campaign to win the GOP nomination,” the Examiner reports. “In July, a month after Trump launched his campaign and watched his poll numbers climb to the top of the field, CNBC’s John Harwood said on Twitter that he didn’t think Trump could win the nomination.”

Harwood has said publicly that Trump “lacks the capacity” to inspire a groundswell similar to the third-party run Ross Perot generated in 1992, the report notes.

Trump has clashed previously with debate moderators, including a widely publicized beef that apparently continues between Trump and Fox News’ Megyn Kelly.