Fight Over Rice Exposes Tensions Between Obama and McCain If there was still any thought that President Obama and Senator John McCain might eventually move past their once-bitter White House rivalry toward a cooperative governing agenda, it was all but dashed on Wednesday. The two men who battled for the presidency four years ago spent the day bumping chests and marking their turf over the attack on the United States consulate in Benghazi, Libya, and the possibility that Mr. Obama might soon nominate Susan E. Rice, his ambassador to the United Nations, as his next secretary of state. Mr. McCain, Republican of Arizona, began the ping-pong volley of sharp-edged commentary in the morning, calling Ms. Rice "unqualified" to serve as secretary of state for her public statements about the September attack in Benghazi. He vowed that he and Senator Lindsey Graham, Republican of South Carolina, would do anything "within our power" to block her appointment. The president responded at a news conference in the afternoon, accusing Mr. McCain of trying to "besmirch" Ms. Rice's reputation and daring him to "go after me" if he wants to. Mr. McCain then took to the Senate floor to denounce the administration's handling of the Benghazi attack and to call for a select committee to investigate. He accused the president and his staff of misleading Americans about the events in Benghazi and said Mr. Obama has created a "credibility gap" with the public on the issue. "I hope the president has no illusions about our view of his responsibility," Mr. McCain said, adding that "we intend to pursue this until the American people have the answers they deserve." Wednesday's back-and-forth recalled the angry messages that dominated the final weeks of the 2008 campaign. Then, the political rivals could hardly speak of each other without the kind of contempt that is bred by a hard-fought election. That animosity softened in the immediate aftermath of the president's first victory. In the early days of Mr. Obama's presidency, Mr. McCain often seemed conciliatory and even warm toward the man who had just beaten him. "I remind all my colleagues: we had an election," Mr. McCain said in early 2009 as he warned his Senate colleagues not to delay the confirmation of Senator Hillary Rodham Clinton to be Mr. Obama's first secretary of state. I think the message the American people are sending us now is they want us to work together, and get to work. Mr. Obama was lavish in his praise of Mr. McCain at the time. At a dinner two days before his inauguration, Mr. Obama called his rival a hero and hailed him as a likely bipartisan partner. "There are few Americans who understand this need for common purpose and common effort better than John McCain," Mr. Obama said. It is what he has strived for and achieved throughout his life. It is built into the very content of his character. Four years later, the tone couldn't be more different. Mr. McCain has occasionally praised the president - for his speech following the shooting of Representative Gabrielle Giffords, and after the killing of Osama bin Laden. But over the course of Mr. Obama's presidency, Mr. McCain has evolved into one of the administration's most aggressive critics, frequently challenging the president on tax policy, the conduct of the war on terrorism and the withdrawal of troops from Iraq and Afghanistan. Far from returning to being the "maverick" in the Senate who annoyed his fellow Republicans, Mr. McCain has embraced his role as staunch partisan. And now, he has become the self-declared leader of the Republican criticism of the administration's handling of the attack in Benghazi. In particular, Mr. McCain has focused his ire on Ms. Rice for offering what the senator calls misleading assessments of the attack in the days after it took place. Mr. McCain and Mr. Graham have been needling the president about Ms. Rice for weeks in television interviews. On Wednesday, it seemed that Mr. Obama had had enough. "If Senator McCain and Senator Graham and others want to go after somebody, they should go after me," the president said, his jaw firmly set. He added: "To besmirch her reputation is outrageous. And, you know, we're after an election now. The reference to the election may have been a subtle hint to Mr. McCain that the president feels more freedom to stand his ground now that he no longer faces the pressure of another trip before the voters. Mr. McCain, likewise, won re-election to another six-year term in 2010 and is a long way away from another campaign. During the news conference, Mr. Obama cited Mr. McCain by name as one of a handful of Republicans who have supported comprehensive immigration reform in the past. But the reference was a passing one that did little to suggest the two men might move toward a cooperative relationship. Instead, the two men seem likely to remain prickly adversaries, particularly on foreign policy, as they wind down their political careers. Bill Burton, a former deputy press secretary for Mr. Obama, suggested in a tweet that Mr. McCain's speech on the Senate floor on Wednesday conjured the image of a cranky old man speaking to annoying kids and "demanding they get off his lawn." Mark Salter, Mr. McCain's former speechwriter and senior adviser, took issue with Mr. Burton's comments, saying: "I'll leave it to the president and to Bill and the other kids in his service to make juvenile rejoinders that cause people to wonder about the state of their relationship. Who cares. Mr. Salter said that Mr. McCain and Mr. Graham and other have legitimate reasons to oppose Ms. Rice as the next secretary of state, if Mr. Obama nominates her. "The president has his job to do and the senator has his," Mr. Salter wrote in an e-mail. They have different views, serve in different branches, and will, unsurprisingly, disagree from time to time, and Bill, not to mention the president, ought to learn to keep their cool when that happens. Those disagreements seem likely to happen quite a bit during the next four years. Correction: November 15, 2012 Because of an editing error, an earlier version of this post incorrectly identified Senator Lindsey Graham's home state. It is South Carolina, not Florida.