New Hampshire Gov. John Lynch (D) announced Thursday that he will not seek reelection in 2012, paving the way for what is expected to be a competitive open seat race.

Lynch, who in his fourth two-year term is already New Hampshire’s longest-serving governor, said the state needed to try somebody else.

“I will keep working hard every day for the next 16 months to serve the people of our state, but I will not run for re-election as Governor of New Hampshire,” Lynch said.

Lynch’s exit comes well before the June filing deadline, but candidates are expected to enter the race in short order.

Ovide Lamontagne, who was the GOP nominee for governor in the 1990s and ran as a tea party candidate for Senate last year, is expected to run. And former state senator Maggie Hassan (D) is also seen as a likely candidate.

Other potential candidates include former state legislator Kevin Smith (R), 2010 GOP gubernatorial nominee John Stephen, former Bureau of Securities Regulation director Mark Connolly (D) and Portsmouth Mayor Steve Marchand (D).

Democrats said they were confident that voters would prefer another Democrat.

“In the coming months, we will have a discussion about who is best fit to fill Gov. Lynch’s shoes and combat the Republican extremists who have tried to take New Hampshire backward,” Democratic Governors Association Chairman Martin O’Malley said.

On the GOP side, Smith was quick to stake his claim after Lynch’s decision.

“I think Concord needs a fresh, conservative voice and a bold, new vision to fundamentally challenge the status quo in state government,” Smith said. “After eight years of stale ideas from the Corner Office, now certainly isn’t the ime to elect career politicians or candidates.”

(And for more on this contest, see our piece from Saturday.)

Despite Smith’s sentiments, Lynch will wind down his tenure as one of the most popular governors in the country, and at just 58 years old he could have still have plenty of his political career in front of him. At the same time, he has shown little interest in national politics.