WASHINGTON - In one week, John McCain brokered a compromise to avoid paralysis in the Senate over President Obama's nominees, introduced banking legislation with Democrat Elizabeth Warren and publicly disputed some Republicans' approach to raising the U.S. debt ceiling.

McCain, who championed the Senate immigration measure that's a major part of Obama's agenda, also has been a frequent visitor to the White House. He's met Obama there at least three times in the past two months and had conversations with White House aides every few days.

The fifth-term Arizona senator said there's "nothing unusual" about his partnerships and compromises with Democrats, which he likened to his willingness to defy Republican President George W. Bush and his defense secretary, Donald Rumsfeld.

"Everybody said when I called for Rumsfeld's resignation, when I voted against the tax cuts and all that, I was the brave maverick," McCain said in an interview at the Capitol. "And then when I was against President Obama, I was the angry, bitter old man. I'm the same guy, OK?"

The senator, 76, has become Obama's strongest Republican ally on Capitol Hill, in a major shift from the acrimony that marked their relationship during and just after their 2008 White House race.

"I'm going to reluctantly have to agree that he's changed," said Jim Manley, a former aide to Senate Majority Leader Harry Reid, a Nevada Democrat. "At a crucial time in the Senate, he's been one of the few Republicans willing to sit down and negotiate compromises with Democrats."

McCain's critics have suggested that the often short-tempered lawmaker is trying to reclaim his "maverick" image in the twilight of his political career to erase damage to his legacy resulting from his choice of Sarah Palin as his 2008 vice presidential running mate.

McCain also had been criticized for moving to the right in his 2010 primary challenge from former Congressman J.D. Hayworth, who accused McCain of supporting "amnesty" for illegal immigrants.

In December 2010, McCain called it a "very sad day" when the Senate voted to repeal the military's policy banning openly gay and lesbian service members.

McCain is a natural fit for negotiating in part because the Senate's top two Republicans - Kentucky's Mitch McConnell and John Cornyn of Texas - are facing primary rivals in their 2014 re-election bids.

Over his 25-year Senate career - and 2000 and 2008 White House bids where he traveled the country on his "Straight Talk Express" campaign bus - McCain cultivated a reputation as a centrist willing to take on his party.

He was the main Republican sponsor of the 2002 law revising the nation's campaign-finance laws, which McConnell opposes, and was an early advocate of abolishing congressionally directed spending known as earmarks. That eventually became a chief rallying cry of the anti-tax tea-party wing of his party.

In the days just before a July 16 compromise that averted a Democratic threat to strip Republicans of their ability to block Obama's nominees, McCain said he made "phone call after phone call after phone call" to try to resolve the dispute and met with Reid.

The deal that McCain helped broker led to the confirmation of Richard Cordray, Obama's choice to run a consumer financial protection bureau born of the worst recession since the Great Depression. McCain was among 12 Republicans who voted to confirm Cordray while McConnell, Cornyn and other Republican leaders opposed the nominee.

"John McCain is why we are where we are: No one was able to break through but him," Reid said on the Senate floor announcing the deal. It also included replacing two Obama nominees to the National Labor Relations Board; Republicans contended they had been unconstitutionally appointed.

On July 11, McCain paired with Warren - an icon of the Democratic base - to introduce legislation that would create a modern version of the Glass-Steagall Act, the Depression-era measure that separated commercial and investment banking.

"Senator McCain has shown real independence and a willingness to take tough stands that I admire," Warren said in an emailed statement Wednesday. "Nobody understands how to get things done in Congress better than he does."