"I don't think there's any doubt that when the president's polling numbers are low that it harms the Republican Party in general, but I think that when it comes election time that the overwhelming majority of Americans will choose their candidate on the basis of that individual candidate's qualifications, vision and record," McCain said in an interview with The Associated Press.
The president's numbers have fallen largely because of his stewardship of the Iraq war. On Tuesday, 11 moderate House Republicans met with Mr. Bush at the White House and bluntly told him that the war was unsustainable without public support and that it was damaging GOP political fortunes.
McCain, a four-term Arizona senator, said that despite what he called Mr. Bush's mismanagement of the war, "there's no doubt that, in my view, the president's not given credit for a healthy economy" or that there hasn't been another terrorist attack on the United States since Sept. 11, 2001.
"But life isn't fair," McCain said as he relaxed with a cup of coffee in the lobby of a hotel near the Gerald R. Ford International Airport. He campaigned in Michigan on Wednesday and Thursday before heading to Chicago on his way back to Washington. He was in Chicago Thursday for fundraisers, including one at a private downtown club.
He said voters not only consider candidates' qualifications and experience but also their performances in presidential debates.
McCain, without mentioning him by name, chided former Massachusetts Gov. Mitt Romney during a Republican presidential campaign debate last week over comments Romney made earlier about terrorist leader Osama bin Laden.
Romney had said "it's not worth moving heaven and earth, spending billions of dollars, just trying to catch one person" and advocated a broader strategy to defeat Islamic jihadists. McCain called the bin Laden comment "naive."
At the debate, Romney defended himself, saying "it's more than Osama bin Laden. But he is going to pay and he will die." McCain shot back that bin Laden was responsible for the deaths of thousands of innocent Americans and "we will bring him to justice and I'll follow him to the gates of hell."
"We cannot allow a person to slaughter innocent Americans and not be dedicated to doing whatever is necessary to bring that person to justice," McCain said Thursday, explaining his debate comment.
The Rev. Al Sharpton, a former Democratic presidential candidate, said Monday that "those of us who believe in God" will defeat Romney for the White House. Sharpton denied he was questioning the Mormon's own belief in God but Romney, while campaigning Wednesday in Iowa, called the remark "bigoted."
Asked whether he agreed with Romney about what Sharpton said, McCain said, "I don't usually examine" Sharpton's comments, adding that he doesn't believe Romney's religion is a factor in the race.
"I do not believe that the fact that Governor Romney is a Mormon will have the slightest impact — nor should it have any impact — on the judgment of the American people as to who their president should be," said McCain, an Episcopalian. "I soundly reject that notion."
McCain also reiterated that he believes it should be up to states to decide the legality of marriage and civil unions for gay couples, which he personally opposes, but that it is all right for such couples to "engage in legal agreements and contracts."
These could include agreements in which one partner can make health decisions in the event the other one becomes too ill to do so.