Lewandowski has been huddling with New Hampshire political operatives and confidants in recent weeks -- joined in some meetings by his wife -- as he mulls a potential Senate bid in the Granite State, multiple sources familiar with the discussions said. He now appears to have his former boss's blessing, a voice that could help sway Republican primary voters.

Lewandowski never joined the White House, but has remained an influential voice in Trump's ear, serving in his kitchen cabinet of informal outside advisers.

"I think he would be fantastic," Trump said of his former campaign manager in a radio interview on Wednesday. "I don't think he's made that decision yet. I will say this -- if he ran, he would be a great senator. If he ran and won, he'd be a great senator. He would be great for New Hampshire. He would be great for the country."

But a Lewandowski candidacy would also exhume a slew of controversies.

Read More