MANCHESTER, N.H. – President Donald Trump encouraged his former campaign manager to continue exploring a Senate bid, praising Corey Lewandowski as a “tough” and “smart” candidate who would be “tough to beat,” but stopped short of formally endorsing him at a campaign rally here Thursday evening.

“Corey, let us know please,” Trump said, leaving the door open to the possibility and teasing a decision soon. “He would be fantastic.”

Lewandowski is widely rumored to be considering challenging incumbent Sen. Jeanne Shaheen, D-N.H., next year, but he made no such announcement tonight.

Lewandowski, who lives in New Hampshire, greeted the president as he landed at the airport here this afternoon and rode to the SNHU Arena in the motorcade. He and his family were expected to discuss the potential Senate run with Trump aboard Air Force One, according to a source familiar with the meeting who was not authorized to speak publicly.

Earlier in the day, Trump offered a stamp of approval to his former aide in a local radio interview. “If he ran and won, he’d be a great senator. He would be great for New Hampshire,” he said.

Trump reiterated his admiration when talking to reporters before taking off for the Granite State Thursday, stressing that Lewandowski was still mulling his options.

All day, the Trump campaign signaled there were no formal plans for Lewandowski to speak at tonight’s rally, but there was always the possibility the president would bring him up to the stage. In the end, Lewandowski was not invited up by his former boss.

Lewandowski was Trump's first campaign manager during the 2016 campaign, but he was fired six months later and eventually replaced by Paul Manafort. Lewandowski is perhaps best known for coining the catchphrase: “Let Trump be Trump.”

He remains close with the president and though he is not working officially with the Trump campaign this cycle, he and David Bossie — another longtime adviser — consistently travel with Trump aboard Air Force One when traveling to various political rallies.

On Thursday, hours before the political rally was set to begin, the House Judiciary Committee announced it had served Lewandowski a subpoena to testify before Congress in September. Chairman Jerry Nadler said the committee wants to question Lewandowski and former White House Deputy Chief of Staff for Policy Rick Dearborn because they were “prominently featured in the Special Counsel’s description of President Trump’s efforts to obstruct justice.”

It’s unclear whether the White House will try to intervene and exert executive privilege on questions concerning specific conversations with the president, as it has in the past.

“Mr. Lewandowski has voluntarily appeared before and cooperated with Congress three times, answering questions for hours. He also has spoken for hours with the Special Counsel’s office,” his lawyer Peter Chavkin wrote in a statement to NBC News. “In light of this, it is fair to ask what could be gained from requiring him to appear yet again.

As usual, during his hour-long re-election pitch, Trump decried “fake witch hunts” but did not mention the new subpoenas specifically.