GREGG AGREES TO JOIN CABINET…. The official introduction of Judd Gregg as the next Commerce Secretary is expected around 11 a.m. (eastern).

Sen. Judd Gregg will be nominated as the new Commerce secretary Tuesday morning, giving President Obama a fresh independent voice in his Cabinet but at a huge cost to Republicans and the larger Senate.

The run-up to the nomination has focused on backroom deals, from New Hampshire’s statehouse to Washington, to preserve the balance of power in Congress. And Tuesday’s White House announcement is expected to be accompanied by one by New Hampshire Gov. John Lynch that will ensure that Gregg’s seat won’t switch to the Democrats before the 2010 elections.

Gregg will be the third Republican to join the Democratic president’s administration. If you were wondering when the last time a president added three members of the rival party to his cabinet, it hasn’t happened in more than a century — Sam Stein reports that Obama will be “the first president since Theodore Roosevelt to appoint three members of the opposing party to his cabinet.”

One can only assume that this one will “count.” In November, the Politico‘s Jonathan Martin said keeping Robert Gates on at the Pentagon wasn’t enough because Gates “is not a sharply partisan figure.” Dan Bartlett, George W. Bush’s former communications director, added, “Choosing one or two token Republicans in lesser Cabinet positions won’t pass the smell test.”

I assume the political establishment is satisfied with three?

As for the next move, CNN reports that New Hampshire Gov. John Lynch (D) will appoint Republican Bonnie Newman to the seat. Newman was most recently the interim president of the University of New Hampshire, but in politics, she’s served as Gregg’s chief of staff, in addition to work in the Reagan and H.W. Bush administrations.

We don’t yet know what Newman’s ambitions are, or whether she has any intention to seek a full term in 2010. If she chooses not to run — Newman has never run for elected office — the odds of a Democratic pick-up are quite good. Josh Kraushaar notes the “limited GOP bench” in the Granite State, and the most likely Republican candidates appear to be former Sen. John Sununu (who lost in 2008) and former Rep. Charlie Bass (who lost in 2006). The leading Democratic candidate is Rep. Paul Hodes, who had expressed interest in the race before Gregg agreed to join Obama’s cabinet, and is even more likely to run now.

Post Script: It seems like a tangent, but we also don’t yet know whether Gregg will cast a vote on the stimulus package. If he does vote, and rejects his new boss’ economic rescue bill, it’ll look kind of ridiculous. If he votes for it, passage is far more likely. And if he gives up his seat in advance of the vote*, Republicans may find it more difficult to sustain a filibuster. Something to keep an eye on.

* edited for clarity

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.