"Clearly Judd and I don't agree on every issue, most notably who should have won the election," Mr. Obama said with Gregg and Vice President Joe Biden at his side. "But we do agree on the urgent need to get American businesses and families back on their feet. We see eye to eye on conducting the nation's business in a responsible, transparent and accountable manner."
If confirmed by the Senate, Gregg would complete an administration team charged with steering the nation out of a recession now in its second year and take over a sprawling Commerce Department tasked with job creation. He also would be the third Republican in the Democrat's Cabinet, joining Defense Secretary Robert Gates and Transportation Secretary Ray LaHood.
In remarks in the White House Grand Foyer, Gregg called Mr. Obama's stimulus plan "bold and comprehensive," reports CBS News White House correspondent Mark Knoller.
"This is not a time for partisanship," said Gregg. "This is a time to govern and govern well." (Read the full text of remarks by Mr. Obama and Gregg)
Gregg added he felt that when the president asked him to serve as Commerce Secretary, "I believed it was my obligation to say yes and I look forward to it with enthusiasm."
Mr. Obama initially had tapped New Mexico Gov. Bill Richardson for the Commerce job, but he withdrew his nomination amid a grand jury investigation into a state contract awarded to his political donors.
After a monthlong search, Obama settled on the 61-year-old Gregg, a former New Hampshire governor who previously served in the House. Gregg has been in the Senate since 1993 and currently serves as the top Republican on the Senate Budget Committee.
New Hampshire Gov. John Lynch, a Democrat, has agreed - in a deal struck with Gregg - to name a Republican to fill the Senate seat.
"I have made it clear to the Senate leadership on both sides of the aisle and to the governor that I would not leave the Senate if I felt my departure would cause a change in the makeup of the Senate," Gregg said on Monday in a statement.
Lynch also confirmed the "understanding," stopping just short of promising to appoint a Republican or an independent to serve out the remaining two years of Gregg's term.
Gregg, as Congressional Quarterly points out, actually voted to abolish the Commerce Department in 1995 while on the Senate Budget Committee. He later showed greater interest than many other Republicans in funding some Commerce agencies.
Knoller reports that during the announcement today, Gregg also specifically thanked Lynch "for his courtesy and courage in being willing to make this possible through the agreement that we have relative to my successor in the Senate."
Gregg said in a conference call with reporters he will remain in the Senate until he is confirmed.
Financial records show that in 2007, Gregg was worth between $3.1 million and $10.5 million, not out of line with others in the Senate. He owns stock in blue chip companies such as Verizon, Exxon, drugmaker Bristol Myers, General Electric, Citicorp, Microsoft, Heinz, Capital One and Bank of America. Some of his larger assets include real estate in New Hampshire, Florida, New York and Massachusetts. He also owns stakes in several software makers. And he's a trustee of the Hugh Gregg Family Foundation, a charitable trust.
Democratic officials say Lynch intends to select Bonnie Newman, Gregg's former chief of staff, and that she intends to step down rather than run in 2010 for a full term. That would create the possibility of a highly competitive race for a seat that long has been in Republican hands.
Choosing a Democrat would have expanded the party's majority in the Senate, moving it closer to a filibuster-proof majority. Gregg had indicated he wouldn't leave the Senate if his departure disrupted the balance of power.
The White House's exact role in the deal that led to Gregg's nomination is unclear.
In a statement, Lynch said the White House was at least directly aware that a deal had been made: Gregg would only become Commerce secretary if he was replaced by a Republican in the Senate.
Yet before Gregg's nomination had become official, Obama spokesman Robert Gibbs said the White House has no part in "picking senators in states that need new senators."
On Sunday, Senate Minority Leader Mitch McConnell appeared on CBS News' Face The Nation and said he was confident the expected appointment of Gregg would "have no impact on the [Senate's] balance of power."
"Senator Gregg has assured me that if this were to happen, it would not change the make-up of the Senate," McConnell told CBS News senior Washington correspondent Bob Schieffer. "Whoever is appointed to replace him would caucus with the Republicans."
Pushed by Schieffer as to whether that will definitely be the case, McConnell reiterated that Sen. Gregg had told him his appointment would "not alter the make-up of the Senate in terms of the majority and the minority."
The deal gave Mr. Obama his top choice for a team tasked with steering the nation out of recession. Republicans get to keep Gregg's seat for two more years, retaining the crucial 41 Senate seats they need to filibuster majority Democrats.
And Democrats, who control 56 seats and caucus with two independents, stand a better chance of flipping Gregg's seat into their ranks in two years by running a candidate against his rookie replacement or an empty seat than Gregg himself.