Ending months of speculation, New Hampshire’s popular Republican Gov. Chris Sununu announced Tuesday that he will seek a third term in 2020 instead of challenging Democratic Sen. Jeanne Shaheen.

Sununu’s decision makes him the clear favorite to retain the governor's office in Concord, but it also leaves the GOP without a top-flight candidate to challenge Shaheen, a former governor who’s seeking a third six-year term representing the crucial battleground state in the Senate.

CHRIS SUNUNU HANDICAPS THE 2020 CONTENDERS

Republicans currently control the Senate 53-47 but are defending 22 of the 34 seats up for grabs in 2020.

In his announcement, made in a Medium post and in an email to his supporters on Tuesday evening, Sununu slammed Shaheen, the senior member of New Hampshire’s all-Democratic congressional delegation.

“We all know that I would defeat Jeanne Shaheen, but others can too,” Sununu touted. “Never before has a sitting twelve-year Senator from New Hampshire accomplished so little.”

Shaheen’s Senate office had no immediate comment when asked about the attack by the governor.

Sununu, who enjoys some of the highest approval ratings of any governor in America, touted his record, saying he’s “getting the job done ... more people are working today in New Hampshire than at any time in history. We have one of the lowest unemployment rates in the nation.”

The governor also took aim at Democrats who won back majorities in the state House of Representatives and Senate in last year’s elections, saying his political opponents' agenda "has become more radical than any of us ever believed possible."

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Longtime New Hampshire Democratic Party chairman Ray Buckley, a vocal Sununu critic, pointed to the governor’s strong support of President Trump as he reacted to Sununu’s 2020 news.

“While we regret missing the opportunity to retire Chris Sununu in a campaign for U.S. Senate, we look forward to replacing him as Governor in 2020, along with his mentor, Donald Trump, Buckley said. “After four years of enriching himself and leaving New Hampshire families in the dust, Chris Sununu will face a successful and strong challenger.”

Sununu, 44, is currently the second youngest governor in America. He's the son of former New Hampshire Gov. John H. Sununu, who later served as chief of staff to President George H.W. Bush, and the younger brother of John E. Sununu, a former New Hampshire Republican congressman who defeated Shaheen in a hotly contested 2002 Senate race before losing the rematch six years later.