It’s as though Sen. Judd Gregg (R-N.H.) never left.

Nearly one month after reversing his decision to resign from the Senate and serve as President Barack Obama’s Commerce secretary, Gregg is back doing what he does best — acting as a top adviser to the Senate Republican leadership and working with the Democrats on pressing issues.

Despite his brief flirtation with a Democratic White House, Senate Republicans welcomed Gregg back with open arms and reoutfitted him with his previous policy and leadership portfolios. The Democrats, too, looked past the momentary embarrassment Gregg caused the Obama administration, engaging fully with him since his return.

“They’ve just been really, really decent. I mean, I’ve received just a very positive response — not only on the Republican side but from the folks I work with on the Democratic side. Everybody’s been very decent,— Gregg said late last week during a 30-minute interview with Roll Call in his Capitol Hill office.

Jokingly, Gregg pointed out that, “I was gone for a week and they spent $1 trillion, so I had to come back,— before adding seriously: “In many ways it was surprising how nice they were. And, it obviously made me feel good that they had the respect for me to say — to welcome me back in such a positive way.—

In a wide-ranging and candid discussion, Gregg affirmed his intent to retire next year upon the conclusion of his third term, praised Senate Majority Leader Harry Reid’s (D-Nev.) management of the chamber, and blasted Obama’s federal budget proposal as a looming impediment to a national economic recovery.

Gregg, 62, appears more like an ambitious Senator in the opening chapter of his career than one staring into the twilight and whose last election is behind him.

He is the ranking member on the Budget Committee, serves as a key adviser to Senate Minority Leader Mitch McConnell (R-Ky.) and is one of four Republicans on an eight-member, bipartisan heath care task force. That panel, led by Finance Chairman Max Baucus (D-Mont.), is charged with drafting the legislation to overhaul health care that Obama has demanded be passed by year’s end.

“I don’t intend to spend the next two years just sitting around as a potted plant,— said Gregg, a former House Member. “I still want to govern. I’m generally in the belief that we need to govern, especially in this time. We’ve got such big problems. We’ve got to address them.—

Among Gregg’s chief concerns are trillions of dollars in projected out-year federal deficits and the need to reform Social Security and Medicare. On this front, the Senator offers a mixture of praise and criticism for Obama while opening a window into an administration he was loosely affiliated with for a couple of weeks in early February.

Having already made the decision to retire from the Senate, Gregg said he was attracted by Obama’s offer to serve as Commerce secretary partly for the professional challenge and because he and the president are on the same page in terms of several goals they share on reform. Particularly on the need to overhaul federal entitlement programs and how to tackle the financial crisis, they agree, the Senator said.

Gregg described Obama’s team as “extremely bright and talented,— saying about the president specifically: “I was really stunned at his perceptiveness on issues, because these were issues I’ve been working on for a long time. … I was just very impressed with how quickly he had a pretty strong opinion and the well-founded thought process as to how he got his opinion.—

Though pleased with the pragmatic approach Obama has taken with Iraq and Afghanistan, Gregg said ultimately he had to terminate his executive branch experiment after he came to believe that Obama was headed too far to the left for him to stomach on key domestic fiscal issues. Gregg, a former governor, said it took about a week for it to sink in that he had made a mistake.

The Senator takes full responsibility for killing his nomination, explaining that he would have been unable to fulfill the part of a Cabinet secretary’s job that requires 100 percent support of the president’s agenda.

“I think the president’s used the right language on a lot of big issues. In fact, when we were talking about this issue of my going down there and being in his Cabinet, that was one of the things that attracted me,— Gregg said. “The problem is … the devil is in the details. … It would have been terrible for me to be [Commerce secretary] right now when they sent the budget up. I mean, really, how would I have felt in that position?—

Gregg characterized Obama as “driving a pretty left agenda— on domestic issues, expressing concern that the president’s budget proposes to nationalize a large portion of the American economy. Among Gregg’s chief worries is Obama’s plan to raise taxes and then use that money to permanently mushroom the size and scope of government.

“This is a pretty broad intrusion of the federal government, probably the broadest in our history — or at least a proposed intrusion — all built around a tax burden which is already very progressive, but is going to be made so much more progressive … that you’re going to reduce the incentive of the entrepreneur to take risk,— Gregg said.

“And, they’re going to undermine the willingness of people to bring capital into the United States because of the cost they’re going to put on that capital,— Gregg continued. “Unlike [former President Bill Clinton], who, when he expanded revenues … directed [them] at driving the deficit down, the Obama administration’s tax increases are directed at exploding the size of government.—

Gregg praised Reid’s management of the Senate thus far in the 111th Congress, which features a Democratic majority of at least 58 seats — at 41, the GOP holds the minimum number of seats required to mount a filibuster. The Senator was equally complimentary of his Republican colleagues’ use of power as afforded to the minority by Senate rules.

The New Hampshire Republican said Reid has worked hard to operate the Senate in a traditional manner, which means the minority has received an opportunity to amend legislation. Gregg credited Reid with allowing action on amendments that at times create difficult votes for Democrats to take, while also lauding the Republican Conference for keeping amendments on point and not abusing Reid’s decision.

The real test for whether Reid is truly running a “traditional— Senate, Gregg said, will be determined by the appropriations process. If future appropriations bills are moved across the floor individually, that will signal that the Senate is once again operating according to regular order.

Gregg said his Conference continues to “wrestle— with its role in the opposition. Republicans, he said, sincerely want to find common ground and work with Senate Democrats and the Obama administration to solve problems. But they have no intention of standing by passively to allow the implementation of policies they believe are bad for the country.

“I greatly respect what Harry Reid is doing right now. … Harry deserves a lot of credit for being willing to step back — not step back but step forward and say, we’re going to try and run the Senate in a traditional way,— Gregg said. “I think Republicans have been respectful of the process. We haven’t been offering a whole panoply of red meat — you know, gotcha amendments.—

After three decades in politics, Gregg said he is at peace with his decision to retire in 2010. The Senator didn’t reference any particular reason for leaving after three terms, other than to say 30 years is long enough.

With the Granite State’s political winds blowing in favor of the Democrats during the past few election cycles, it has been suggested that Gregg chose to retire to avoid a difficult and costly re-election battle. And in fact, the Senator noted that the Democratic Party in New Hampshire remains institutionally and operationally stronger than the state GOP, which he referred to as a “cottage industry.—

Gregg said he does not plan to be active in helping to identify a Republican to run for his vacated seat, explaining that he doesn’t have to, given the strong bench of candidates examining a run.

“At some point you’ve got to say, [you’ve] done what you can, and hopefully you’ve made some progress. We have made progress, in many areas that I think are important,— Gregg said. “Now, whether we’ll get the ball across the finish line, I don’t know. But clearly, the opportunity is sitting there.—