Obama already owes McCain for brokering the deal last month that allowed the president to overcome Republican objections and fill seven top administration jobs.
And McCain joined four Democrats and three Republicans in drafting the Senate's landmark bill to overhaul U.S. immigration laws, a top Obama priority.
So popular has the Arizona Republican become among Democrats that Senate Majority Leader Harry Reid—who in 2008 said, "I can't stand John McCain"—now describes him as a "great senator," right up there with the late Ted Kennedy, the Democratic "lion of the Senate" who became a bridge between parties after his own presidential ambitions were crushed.
"He's become our go-to guy," a senior Democratic aide said of the 76-year-old white-haired senator.
That's an exaggeration. McCain remains a critic of Obama's handling of the deadly attack on a U.S. diplomatic mission in Benghazi, Libya, last September and of what he considers the "disgrace" of Obama's non-intervention in Syria.
But on domestic issues, McCain has emerged as one of the top deal makers in Washington, a Republican Obama can do business with.
Moving toward the middle
McCain said in an interview that he has been able to work more with Obama in part because the president has moved toward the middle in his second term and become more willing to negotiate.
McCain has also moved toward the middle after having veered toward the right in 2010 when he survived a Republican primary challenge and won election back home in Arizona to a fifth, six-year Senate term.
Two unrelated events have helped as well: McCain's new friendship with Charles Schumer, the third-ranking Senate Democrat who worked with McCain on the immigration bill, and Obama's choice of a McCain friend, Denis McDonough, as White House chief of staff.
The three have clicked.
At a time when the top congressional Republicans, Senate Minority Leader Mitch McConnell and House of Representatives Speaker John Boehner, rarely communicate with the White House, McCain does.
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He said he and McDonough talked three times a day during the negotiations over Obama's stalled nominations.
"With all due respect to his predecessors, Denis knows how the Senate works," McCain said of McDonough, whom he knows from McDonough's days as a senior aide to former Democratic Sen. Tom Daschle.