It’s been a year since Sen. Judd Gregg (R-N.H.) nearly joined President Barack Obama’s Cabinet as Commerce secretary. And while he continues to work across the aisle on some key issues, he has also emerged as one of the Republican Party’s most ardent and effective White House critics.

Gregg, 62, is retiring this year after having served 18 years in the Senate and three decades in public office. But that hasn’t stopped the New Hampshire Republican and ranking member on the Budget Committee from waging a war against some of Obama’s top priorities. From the president’s $787 billion economic stimulus package to health care reform to the 2011 budget blueprint, Gregg hasn’t minced words while helping to lead the opposition of a determined Senate minority.

But even as he accuses Obama and the Democrats of proposing “a government takeover of health care” and “leading our nation into a position of insolvency,” Gregg still works closely with Senate Democratic leaders and the White House on several controversial issues.

There appear to be two sides of Gregg, and that may explain both Obama’s decision to nominate him for the Commerce job in the first place and why Gregg abruptly decided to withdraw from consideration.

In an interview Wednesday morning in his office in the Russell Senate Office Building, Gregg laughed as he described his memory of the nomination as a “trauma.” He said he has no regrets about removing himself from consideration but was contrite about the public embarrassment his waffling caused the White House. Essentially, Gregg said he should have known better.

“On reflection — especially as I watched the stimulus evolve, I realized what was coming on the budget side — I recognized that it would be very hard to be supportive of the administration’s positions on fiscal policy if they were going to go into this massive expansion of the government, which it’s pretty obvious they were going to do,” Gregg said. “And of course with the health care package it would have been impossible because I think that’s a disaster fiscally and I think it’s a disaster from the standpoint of the quality of health care in this country.”

[IMGCAP(1)]Gregg described his relationship with Obama these days as professionally courteous, saying that the two have had limited interaction but that the president has always been respectful and listened to his ideas. Gregg has long been a go-to guy in the GOP Conference on budget and tax issues, but his decision to stay in the Senate earned him even greater respect from his colleagues, who at the time were reeling from heavy losses in the 2008 elections.

The Senate’s most conservative Republicans would be expected to oppose most, if not all, of the Democrats’ proposals related to health care and the federal budget. But because Gregg has a reputation as a pragmatist — and because he entertained accepting a role in Obama’s Cabinet — many Republicans believe he adds credibility to their arguments. And that, they say, can help the party appeal to independents and even Democrats across the country.

Republican leaders have been content to let Gregg hog the soapbox, as they did again on Wednesday, when the Granite State Senator joined GOP Conference Chairman Lamar Alexander (Tenn.) at a news conference to harangue Obama’s fiscal 2011 $3.8 trillion budget proposal. Predictably, Gregg didn’t pull any punches, describing the president’s blueprint as “malfeasance” and a “failure in leadership.”

National Republican Senatorial Committee Chairman John Cornyn (Texas), who is responsible for chipping away at the Democrats’ 59-seat majority in this year’s midterm elections, called Gregg an “immensely important” asset to the Conference who helps the party score both policy and political points. Cornyn indicated that he uses Gregg as a model for the type of influence that a Senator can wield when he makes his recruiting pitch.

“What somebody like Judd demonstrates is that if you are smart and you know what you’re talking about, you can definitely make a difference up here,” Cornyn said. “That helps motivate good people who want to make a difference, but don’t know how, to run for office and understand the importance of what we’re trying to do here.”

With less than 11 months to go in his third and final term, Gregg, typically, is focused on the needs of his constituents and working on complicated legislation with national implications. The Senator still holds out hope for a bipartisan breakthrough on health care reform — he said such a bill would have to be smaller and take an incremental approach — and is interested in taking one more shot at entitlement reform.

The former governor also wants in on any effort to overhaul the No Child Left Behind law, of which he was a principal author. Obama has called for lawmakers to revisit the act.

Despite receiving the most attention for his outspoken opposition, Gregg said he remains committed to bipartisanship, citing his collaboration with Senate Budget Chairman Kent Conrad (D-N.D.) on deficit reduction and Sen. Jack Reed (D-R.I.) on financial regulatory reform. Gregg and Reed are one of four working groups assembled by Banking, Housing and Urban Affairs Chairman Chris Dodd (D-Conn.) to draft aspects of the financial overhaul.

Meanwhile, Gregg worked to help Obama confirm Federal Reserve Chairman Ben Bernanke to a second term, which had at one point appeared to be in jeopardy, and to defend Treasury Secretary Timothy Geithner, who is under fire for his involvement with the Temporary Asset Relief Program and the stabilization of the financial markets. Gregg also supports the administration’s policies on Afghanistan and India.

“There are areas where I’ve felt they’re doing the right things, and when they have I haven’t hesitated to go out and carry their water,” Gregg said. “But where I do have very distinct disagreements with them, and think that we are truly on the wrong course, [is] on fiscal policy.”