The Democratic field for Senate in New Hampshire is already starting to clear for former governor and 2002 nominee Jeanne Shaheen, who announced this morning that she'll be making the race. The New Hampshire Union Leader reports that Portsmouth Mayor Steve Marchand, one of three Democrats already running, will soon withdraw from the campaign. Marchand had previously indicated that he would drop out if Shaheen ran.

The two remaining Dems, activist Katrina Swett and Dartmouth professor Jay Buckey, don't appear to be withdrawing for now. Swett put out a press release declaring, "I entered this race to make a positive change in the direction of our country and I remain committed to ensuring John Sununu’s defeat November 2008" — a noncommittal statement either way.

Buckey, meanwhile, appears committed to staying in: "I look forward to a vigorous discussion of the important issues in a primary, and I’d welcome Jeanne Shaheen into the race if she decides to run."

Late Update: Marchand formally withdrew from the race on Saturday. He did not close the door on a future race for political office — perhaps a run for Senate in 2010 — but did not seem too eager to address the question just yet: "I've only been an ex-candidate for 15 minutes."