Larry Kudlow, director of the U.S. National Economic Council, speaks during a White House briefing in Washington, D.C., U.S., on Monday, Jan. 28, 2019.

WASHINGTON – White House support for Herman Cain, one of President Donald Trump's controversial Federal Reserve Board picks, seemed to weaken Thursday, when Trump's top economic advisor Thursday pointedly declined to give Cain a full-throated endorsement.

"Yes, we are, at the moment," National Economic Council Director Larry Kudlow replied when asked during an event in Washington about whether the White House still stood behind Cain, a former pizza executive and 2012 Republican presidential candidate.

"He's in the vetting process, we will see how that turns out," Kudlow added. "I don't want to prejudge it one way or the other."

Kudlow's hands-off attitude about the nomination is a stark departure from the traditional role played by White House officials after the president announces his intent to nominate someone to a post like the Fed board, which requires Senate confirmation. Kudlow is a former CNBC contributor.

In most cases, White House officials are expected to act as front-line cheerleaders for the president's picks, making the case to both the Senate and the public that the president's choice was a good pick.

But Cain does not fit the mold of a traditional nominee to the Federal Reserve Board. Although Trump has yet to submit formal nomination papers for him, Cain's chances of winning Senate confirmation have grown slimmer by the day since Trump announced his selection last Thursday.

At least three Republican senators confirmed this week that they would not vote to confirm him to the post: Sens. Lisa Murkowski of Alaska and Cory Gardner of Colorado, and newly minted Utah Sen. Mitt Romney.

There are also concerns among lawmakers and on Wall Street about Trump's other contentious pick for the Fed board, conservative political activist and economics writer Stephen Moore. It is unclear whether Republican senators will vote against Moore, who has had to contend with claims that he is unqualified for the Fed role as well as revelations about his messy divorce. Moore advised Trump during his 2016 campaign and co-authored a 2018 book called "Trumponomics: Inside the America First Plan to Revive Our Economy."