Whether looking at bills they have led on or bills they have signed onto, Mr. McCain has reached across the aisle far more frequently and with more members than Mr. Obama since the latter came to the Senate in 2005.
In fact, by several measures, Mr. McCain has been more likely to team up with Democrats than with members of his own party. Democrats made up 55 percent of his political partners over the last two Congresses, including on the tough issues of campaign finance and global warming. For Mr. Obama, Republicans were only 13 percent of his co-sponsors during his time in the Senate, and he had his biggest bipartisan successes on noncontroversial measures, such as issuing a postage stamp in honor of civil rights icon Rosa Parks.
With calls for change in Washington dominating the campaign, both Mr. Obama, the Democrats' presidential nominee, and Mr. McCain, his Republican opponent, have claimed the mantle of bipartisanship.
But since 2005, Mr. McCain has led as chief sponsor of 82 bills, on which he had 120 Democratic co-sponsors out of 220 total, for an average of 55 percent. He worked with Democrats on 50 of his bills, and of those, 37 times Democrats outnumber Republicans as co-sponsors.
Mr. Obama, meanwhile, sponsored 120 bills, of which Republicans co-sponsored just 26, and on only five bills did Republicans outnumber Democrats. Mr. Obama gained 522 total Democratic co-sponsors but only 75 Republicans, for an average of 13 percent of his co-sponsors.
An Obama campaign spokesman declined to comment on The Times analysis.
McCain campaign surrogate Sen. Lindsey Graham, though, said the numbers expose a difference between the two candidates.
"The number - 55 and 13 - probably shows that one has been more desirous to find common ground than the other. The legislative record of Senator Obama is very thin," said Mr. Graham, South Carolina Republican, who has teamed up with Mr. McCain probably more than any other senator.
The Times study looked at the bills each man introduced as the chief sponsor, and at the bills sponsored by other senators that each man signed onto. The study excluded resolutions and amendments, focusing instead on measures that each man authored and put into the normal legislative process.
Former Sen. James Jeffords of Vermont, Sen. Bernie Sanders of Vermont and Sen. Joe Lieberman of Connecticut, all independents, were grouped with Democrats because each caucused with Democrats during the time under study.
Bipartisanship is a frequent issue on the campaign trail, with the McCain camp and surrogates such as Mr. Graham arguing the standard is how often someone takes leadership on an issue in defiance of his own party - a measure by which Mr. Obama falls short and Mr. McCain clearly excels.
He even revels in his stances, telling the audience at a values forum at Saddleback Church in California last month his list is extensive: "Climate change, out-of-control spending, torture." He could have added campaign-finance overhaul, immigration, a patients' bill of rights, gun control and tax cuts as other areas on which he's broken with the majority of his party.
At the same forum, Mr. Obama said his major break with Democrats came on congressional ethics, when he sponsored a bill to curb meals and gifts from lobbyists.
In a memo to reporters, his campaign points to bills he worked on that gained near-unanimous support from both parties, including a bill more than a third of the Senate signed onto, sponsored by Sen. Sam Brownback, Kansas Republican, pushing peace initiatives in Sudan, and a bill sponsored by Sen. Orrin G. Hatch, Utah Republican, on charitable contributions that passed by a voice vote in each chamber.
But foremost, his campaign cites his work teaming up in 2006 with Sen. Richard G. Lugar, Indiana Republican, on the Cooperative Proliferation Detection Act, a noncontroversial measure to secure weapons of mass destruction, and with Sen. Tom Coburn, Oklahoma Republican, to force the administration to create a searchable database to track federal spending grants.
Speaking to reporters during the Republican National Convention earlier this month Obama aide Robert Gibbs said Mr. Lugar and Mr. Coburn would back up Mr. Obama's bipartisanship claims.
Mr. Lugar's spokesman said the senator is not doing interviews on the subject. Mr. Coburn, in an interview, said Mr. Obama is a good senator to work with, but said there's no comparison to Mr. McCain's long record.
"Barack is a great guy, a nice guy, he's a good friend of mine. He has passed two pieces of legislation since he's been in the Senate - had his name on two," Mr. Coburn said. He praised Mr. Obama's staff for the work they did on the spending grants bill, but he said Mr. Obama hasn't gone head-to-head against his leadership when it mattered: "Where have you seen him challenge the status quo?"
Mr. McCain on the campaign trail cites his own frequent Democratic legislative allies such as Mr. Lieberman, with whom he's worked on gun control and global warming; Sen. Edward M. Kennedy of Massachusetts, who was his partner for immigration and patients' rights; Sen. Russell D. Feingold of Wisconsin, who worked with him on campaign finance; and Sen. Byron Dorgan of North Dakota, who was the top Democrat on the Indian Affairs Committee when Mr. McCain was chairman.
Mr. Feingold, Mr. Dorgan and Mr. Kennedy didn't respond or declined through spokesmen to talk about the issue. Mr. Lieberman, however, has gone in the opposite direction, endorsing Mr. McCain for office and hitting Mr. Obama for failing to live up to his bipartisan claims.
Mr. Graham said it was unfortunate people weren't recognizing their work with Mr. McCain.
"What you've got now is, you've got some people who are afraid to recognize John's bipartisanship because of the nature of the election," Mr. Graham said.
Mr. Graham has teamed up with Mr. McCain on some of his most contentious bills, including the immigration and campaign-finance fights, and said they both have "the scars to prove" they were in the fights.
"I have experienced the price that's been paid to help John do some difficult things since 2004," he said.
Those fights are part of the reason Mr. McCain had trouble securing the Republican presidential nomination, including winning less than 50 percent of Republican primary voters' support, despite clearing the field less than halfway through the primaries.
The Times analysis found Mr. McCain's most frequent Democratic teammates are Mr. Dorgan, with whom he shared leadership of the Indian Affairs Committee and who co-sponsored 23 of Mr. McCain's bills, and Mr. Lieberman, who signed onto 15 McCain bills.
Mr. Obama's most frequent Republican partners were Mr. Lugar, who co-sponsored nine Obama bills, and Sen. Norm Coleman, Minnesota Republican, who signed on to eight of Mr. Obama's measures.
The bill on which Mr. McCain attracted the most support in the past few years was his plan to combat greenhouse-gas emissions. That bill garnered 16 co-sponsors, 14 of whom were Democrats, including Sen. Joseph R. Biden Jr., Democrats' vice-presidential nominee. Mr. Obama himself signed onto another of Mr. McCain's global-warming bills.
Mr. Obama's best successes in attracting co-sponsors came on a bill to boost the union's bargaining power with the Federal Aviation Administration, on which all 38 co-sponsors were Democrats, and a bill to issue a postage stamp honoring Mrs. Parks, which garnered 24 Democrats and 14 Republicans.
The Times study didn't look at voting, but Congressional Quarterly conducts annual studies of senators' voting records.
Over his Senate career, Mr. McCain has voted with the majority of Senate Republicans about 85 percent of the time, while in his three years in the Senate Mr. Obama has voted with his party 97 percent of the time.
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