New Hampshire Gov. John Lynch (D) indicated that he is likely to appoint another Republican to the Senate if President Barack Obama nominates Sen. Judd Gregg (R-N.H.) to be Commerce secretary, in his first public comment on the potential vacancy.

Obama has yet to make Gregg’s nomination official, but an announcement is expected on Tuesday. If Lynch nominated a Democrat to fill Gregg’s seat, Senate Democrats could have a filibuster-proof 60-vote majority.

“I have had conversations with Senator Gregg, the White House and U.S. Senate leadership,” Lynch said in a statement. “Senator Gregg has said he would not resign his seat in the U.S. Senate if it changed the balance in the Senate. Based on my discussions, it is clear the White House and Senate leadership understand this as well.”

In his statement, Lynch did not explicitly say he would nominate a Republican to succeed Gregg, although speculation has centered around his former Chief of Staff Bonnie Newman — a longtime Republican who supported his first bid for governor in 2004.

“If President Obama does nominate Senator Gregg to serve as Commerce Secretary, I will name a replacement who will put the people of New Hampshire first and represent New Hampshire effectively in the U.S. Senate,” Lynch said.

Granite State sources say that whomever Lynch names will likely be a placeholder for two years, setting up an open-seat Senate contest in 2010.