MANCHESTER, N.H. – He flirted for nearly six months with running for the Senate in his home state of New Hampshire, but in the end Corey Lewandowski has decided to pass on making a bid.

Lewandowski, President Trump’s 2016 campaign manager and a frequent cable news surrogate who remains a close outside adviser to the president, took to Twitter on Tuesday to announce that after much consideration he has "decided to forgo a campaign for the US Senate.”

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Taking aim at popular two-term Democratic incumbent Sen. Jeanne Shaheen, the often combative Lewandowski wrote that while “taking on a career politician from the Washington swamp is a tall order, I am certain I would have won. My priorities remain my family and ensuring that @realDonaldTrump is re-elected POTUS.”

The president praised Lewandowski’s potential Senate bid when he held a 2020 reelection rally in Manchester, N.H., in August.

But some establishment Republicans gave Lewandowski the cold shoulder. Former Sen. Judd Gregg, who also served as governor, made headlines during the summer by calling Lewandowski “a thug.”

In media interviews this fall, Lewandowski was all over the board on whether he was moving toward launching a Senate campaign. As for his timing, two months ago he told Fox News and other news organizations that he was "not under this illusion" that he had "to make a decision today or tomorrow. I think time is on our side.”

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Lewandowski, a longtime New Hampshire resident who works as a consultant and lobbyist in the nation’s capital, repeatedly said he would be the best Republican to challenge Shaheen in 2020 because of his fundraising “prowess” due to his close ties to the president.

Three Republicans have already declared their candidacies for the GOP Senate nomination, in hopes of facing off next year against Shaheen, a former three-term governor. They are retired Army Gen. Don Bolduc, former New Hampshire House Speaker Bill O’Brien, and Bryant "Corky" Messner, a self-made millionaire attorney. None of them have come close to matching Shaheen’s fundraising haul. The Democratic incumbent brought in $2.27 in the July-September third-quarter of fundraising, with roughly $4.3 million cash on hand.

The New Hampshire Democratic Party took aim at the three GOP contenders, tying them to Lewandowski.

"Every Republican running for Senate in New Hampshire has stood proudly with Corey Lewandowski and Donald Trump in their efforts to take away health care from tens of thousands of Granite Staters and reverse Roe vs. Wade,” said party spokesman Josh Marcus-Blank.

The last two Senate elections in New Hampshire have been razor thin — Shaheen narrowly defeated former GOP Sen. Scott Brown in 2014 and then-Democratic Gov. Maggie Hassan defeated Republican incumbent Sen. Kelly Ayotte by just 1,017 votes in 2016.

In 2020, national Republicans view New Hampshire as one of the few places they may be able to go on the offense as they mostly work to defend their 53-47 majority in the Senate.

But defeating Shaheen won’t be easy, thanks to her popularity and her formidable campaign war chest.

Fox News' Patrick Ward contributed to this report.