WASHINGTON—Barack Obama likes to say, “We can’t afford to give John McCain the chance to serve out George Bush’s third term.”

Bush’s “third term” has become a favorite attack line for Democrats, repeated almost daily by the candidate and his surrogates. They argue that McCain favors failed Bush administration economic policies and would keep U.S. troops in Iraq for the forseeable future—possibly even longer than Bush is anticipating.

But if McCain is running as a Bush stand-in, it’s news to the McCain campaign and the White House. Although he almost always supported Bush’s positions in Congress, McCain has done his best on the campaign trail to shun the widely unpopular Republican president, whose job approval rating sunk to a record low 28 percent in AP-Ipsos polls in April and July.

The last time the two Republicans were together was a closed-door McCain fundraiser in Arizona back in May. The only photo of the two was a departure shot at the airport. McCain seldom mentions the unpopular president whose job he seeks. The White House rarely talks about McCain.

So far McCain’s strategy hasn’t convinced the public. Six in 10 adults think McCain will follow the policies of Bush, including more than half of whites and nearly six in 10 independents, according to an AP-Yahoo News poll in late June.

McCain has begun airing a television ad in crucial states to defend himself against this perception. An announcer asserts, “We’re worse off than we were four years ago.” Pictures of the White House, the Capitol and the floor of the House of Representatives flash on the screen. The ad calls McCain “the original maverick.”

While McCain spurns Bush as he hunts for general-election votes, the Obama camp melds the two together.

“Four more years of what we’ve had,” warns Sen. Evan Bayh, D-Ind. “More of the same,” echoes former Rep. Jim Leach of Iowa, a moderate Republican supporter of Obama. “The John McCain of 2000 wouldn’t even consider voting for the John McCain of 2008,” suggests Howard Dean, chairman of the Democratic National Committee.

The DNC sends out e-mail messages enumerating “100 Ways McCain and Bush are the Same.”

The strategy plays on Bush’s low approval ratings, public weariness with the Iraq war, high gasoline prices and general economic angst. It challenges McCain’s reputation for independence and helps Obama push his theme of change.

Democrats acknowledge McCain’s maverick past, as when he challenged Bush for the GOP nomination in 2000, but say those days are long gone.

“The price he paid for his party’s nomination has been to reverse himself on position after position,” Obama told a recent town-hall meeting in Indiana. “And now he embraces the failed Bush policies over the last eight years—politics that helped break Washington in the first place. And that doesn’t exactly meet my definition of a maverick.”

McCain did try to shore up his Republican base by promising to extend and expand Bush tax cuts he once opposed. He abandoned his opposition to offshore drilling. He made peace with television evangelists Pat Robertson and Jerry Falwell, whom he once called “agents of intolerance.” And he vowed to appoint judges in the mold of Supreme Court Justices John Roberts and Samuel Alito, both Bush nominations.

But he hardly qualifies as a carbon copy of Bush.

Even now, he opposes Bush’s support for drilling in the Arctic National Wildlife Refuge. Along with Obama, he backs more stem cell research and new restrictions on greenhouse gases that contribute to global warming. He’s slammed the Bush administration’s handling of Hurricane Katrina.