But as a matter of history, it is easier to run as the opposition party if you actually are the opposition party.  “When the president of the United States is from your own party, to present yourself as a change agent is not the easiest thing to pull off,” said Joe Trippi, a Democratic strategist. Referring to Senator Barack Obama, the Democratic nominee, Mr. Trippi added, “All Obama has to do is say, ‘Bush-McCain, Bush-McCain.’ ”  That was certainly a chant never heard in the Xcel Energy Center over the last four days. President Bush canceled his trip here to supervise the response to Hurricane Gustav and addressed delegates only by video Tuesday, before the broadcast networks began their coverage for the night.  Once his image faded from the screen, none of the marquee speakers for the rest of the convention mentioned his name during the nightly prime hour. Indeed, a computer count showed that Democrats mentioned the name Bush 12 times as often at their convention. And delegates on Thursday were shown a video about the attacks of Sept. 11, 2001, that included a picture of Rudolph W. Giuliani and Donald H. Rumsfeld but none of Mr. Bush, whose presidency was singularly shaped by that day.  In his acceptance speech shortly afterward, Mr. McCain thanked “the president,” without naming him, for leading the country “in those dark days” and for “keeping us safe from another attack.” But he made no further reference to Mr. Bush, and when it came to the improved security in Iraq over the last year, he credited “the leadership of a brilliant general, David Petraeus.”  Republicans said Mr. McCain had little choice.  For “every candidate, regardless of whether they’re an incumbent or a challenger,” said Sara Taylor, a former White House political director under Mr. Bush, “one of the fundamental missions is how to set themselves up as the change agent, and John McCain is well equipped based on a long record as a maverick to do that.”  And it is true that even vice presidents running as popular presidents leave office have labored to establish their own identities. “Conventions are always about the next four years, not the last four or eight years,” said Ron Kaufman, who was a top aide to President George Bush. “In the end, whether your party is in power or not, it’s about, ‘What are you going to do for me for the next four years?’ ”  Still, even though the elder Mr. Bush wanted to slip out of Ronald Reagan’s shadow in 1988 and Al Gore tried to distance himself from the scandals of Bill Clinton in 2000, they both used their acceptance speeches to boast of their administrations’ records. And neither ran an advertisement like the one Mr. McCain did last month declaring, “We’re worse off than we were four years ago.”  By the time the convention here was about to get under way, Mr. McCain almost sounded like a speaker at an Obama rally. “I promise you, if you’re sick and tired of the way Washington operates, you only need to be patient for a couple of more months,” he told supporters in O’Fallon, Mo., on Sunday. “Change is coming! Change is coming! Change is coming!”  He continued the mantra Thursday. “Let me just offer an advance warning to the old big-spending, do-nothing, me-first, country-second crowd,” Mr. McCain said. “Change is coming.”  Boasting that he had fought corruption even among Republicans, he said the party had lost its way. And he offered a sweeping promise of reform: “We need to change the way government does almost everything.”  Mr. McCain has been a strong supporter of Mr. Bush on the Iraq war and other issues, providing ammunition for Democrats arguing that his election would amount to a third Bush term. And the Obama campaign signaled it would not cede the change argument, airing another advertisement showing him with Mr. Bush and concluding: “We can’t afford four more years of the same.”  Still, Mr. McCain might be better positioned to make the case than any other Republican, given his reputation for independence and periodic scraps with Mr. Bush. What he needs to change first is the course of a campaign fighting the tide of history. He has 60 days to do it.  A version of this news analysis appears in print on , on Page A1 of the New York edition with the headline: The Party in Power, Running as if It Weren’t. Order Reprints| Today's Paper|Subscribe
Partly by his nature and partly by calculation, John McCain is sounding a call to topple the establishment.