And he’ll be hitting the campaign trail with Obama.

After a prolonged silence through most of the primary season, Sen. Christopher J. Dodd is rejoining the presidential race on somebody else’s team — Sen. Barack Obama’s.

The Connecticut senator, whose own presidential campaign failed to draw enough attention to propel him past the first contest in Iowa, is expected to announce his endorsement of Obama this morning, according to a Democratic official close to Dodd. He’ll then campaign with Obama in Ohio.

Obama’s campaign hopes that the March 4 primaries in Ohio, Texas, Vermont and Rhode Island will be the victory that clinches the Democratic nomination for him. When he faces Sen. Hillary Rodham Clinton in another debate tonight — the last before these pending primaries — he’ll do it with Dodd in his corner.

It’s unclear what Dodd’s task will be with the campaign or whether he’ll be hitting those last two New England states still awaiting primaries next week. But if Obama eventually gets the nomination, Connecticut’s two senators will be in opposing campaigns. Sen. Joseph I. Lieberman is one of Republican Sen. John McCain’s staunchest allies.

What I find particularly interesting is that Dodd is first former Democratic presidential candidate to endorse. Biden, Richardson, Edwards, and Kucinich have all withheld their endorsement until now. In contrast, I think every Republican presidential candidate of note who dropped out of the primary, quickly endorsed another candidate.

Eric Kleefield of TPM Election Central says Dodd will be campaigning with Obama in Ohio.

Update:

The text of Dodd’s email to supporters is here. Obama’s speech accepting Dodd’s endorsement is here.