Arizona Sen. John McCain could understandably be scowling: He could face a more difficult political landscape than any presidential candidate in a generation.

Only 39 percent of Americans have a favorable view of the Republican Party he represents, the latest USA Today/Gallup Poll shows. A record 63 percent say the Iraq war he defends was a mistake. The disapproval rating for President Bush, the incumbent McCain has embraced, has hit 69 percent, the most negative assessment of any president since the Gallup Poll began asking the question 70 years ago.

Yet in what seems to be the most promising election for Democrats since the aftermath of the Watergate scandal three decades ago opened the door for Democrat Jimmy Carter to win the presidency, the USA Today/Gallup Poll shows the presumptive Republican presidential nominee within striking distance of either Illinois Sen. Barack Obama or New York Sen. Hillary Rodham Clinton.

"Sen. McCain will not be a pushover in Ohio," cautions Ted Strickland, the Democratic governor of what has become perhaps the nation's most important electoral state. "It will be a hotly contested race."

At least at the moment, McCain's personal qualities — his stature as a Vietnam War hero, reputation as an independent-minded Republican and persona as a strong leader — are trumping the significant policy disadvantages he faces in pursuing a third consecutive term for the GOP in the White House.

The protracted and increasingly bitter rivalry between Obama and Clinton for the Democratic nomination is a boost for McCain, too.

One in four voters who say the invasion of Iraq was a mistake back him, as do one in four who disapprove of Bush. In a worrisome sign for Democrats, one in five Democrats and Democratic-leaning independents say they'll switch to McCain if the Democrats don't nominate Obama; another one in five say they'll switch if the party doesn't nominate Clinton.