FILE PHOTO: Former Trump campaign manager Corey Lewandowski testifies before a House Judiciary Committee during a hearing on "Presidential Obstruction of Justice and Abuse of Power," in the Rayburn House Office Building on Capitol Hill in Washington, U.S., September 17, 2019. REUTERS/Sarah Silbiger.

(Reuters) - Corey Lewandowski, a close ally of President Donald Trump, on Tuesday said he would not run for the U.S. Senate seat in New Hampshire now held by Democrat Jeanne Shaheen.

The Republican political operative from Manchester, New Hampshire, had weighed a Senate bid after his work running Trump’s presidential campaign in 2016 for a time.

Shaheen, a former governor of the New England state, is expected to seek a third six-year term in the Senate next year. She has also been discussed as a possible Democratic vice presidential pick.

"While taking on a career politician from the Washington swamp is a tall order, I am certain I would have won," Lewandowski said here on Twitter, adding that he would make an endorsement in the race given the need to support Trump's policies on the economy and judicial appointments.

Lewandowski, who has remained close to Trump, did not offer a reason for not joining the race and said he is focused on his family as well as helping Trump’s 2020 re-election campaign.

He would have faced three other Republicans hoping to win a key position representing the northeastern swing state, where Democrat Hillary Clinton beat Trump in the 2016 race by just 2,736 votes.

New Hampshire Democratic Party spokesman Josh Marcus-Blank said in a statement that those remaining Republicans will “tear each other down in the contentious primary Lewandowski has left behind” while Shaheen works to “lower prescription drug costs” and secure benefits for military veterans.