Donald Trump faces the risk that Ben Carson will corner the outsider vote if he wins the Iowa caucus in the race for the Republican presidential nomination, former GOP campaign adviser Kevin Hassett said Wednesday.
Carson recently overtook Trump as the front-runner in a number of polls, just in time for Wednesday night's third Republican debate, sponsored by CNBC. CNBC's full coverage begins at 5 p.m. EDT.
"I think a lot of people are now looking at Iowa, and thinking that Carson's going to win Iowa. Then all of a sudden the nonestablishment people coalesce around Ben," Hassett told CNBC's "Squawk Box." "I think that's the Number 1 threat — near-term threat — to Trump."
For that reason, Trump will likely try to distinguish himself from Carson in Wednesday's debate, Hassett said.
Wednesday night's main forum essentially will highlight two sets of candidates, said Joe Lockhart, former press secretary to President Bill Clinton. One is focused on political outsiders like Carson, Trump and former Hewlett-Packard CEO Carly Fiorina, and the other is between candidates with governing and legislative experience.
In the latter, candidates must still differentiate themselves from Trump, Lockhart told "Squawk Box." "There will be two debates, but Trump will be in the middle of both of them."
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Trump has the most to lose in the debate because he has dominated the campaign narrative, Lockhart said. However, the focus has not been on substantive issues like taxes and health care, but the trading of insults between Trump and the other candidates, he added.
"I expect other Republican candidates will really be trying to put him on the spot and demonstrate that when it comes to policy, he tends to be making it up as he goes along."