Less than a month before Election Day, John McCain’s position is increasingly desperate. Barack Obama has built (or rather, regained) a mid- to high-single-digit lead in national polling over the last two weeks and has significantly improved his standing in most swing states. McCain is more likely to lose on Nov. 4 than to win, and given the enormous built-in advantages that his opponent enjoys—the economy, most importantly—there may not be anything he can do to engineer a victory.

But he’s not doomed in the way that others have been at this same point in recent campaigns. In 1996, for instance, Bob Dole was running about 15 points behind Bill Clinton in early October. And Walter Mondale was lucky to be within 20 points of Ronald Reagan in any poll conducted in early October 1984. For them, victory was totally implausible. For McCain, it is merely hard.

That plausibility, though, may also be a curse for McCain, since it provides him with a powerful incentive to do what he has apparently decided to do: Risk his own reputation on a vicious, personally negative campaign that, if successful, will give him four (or eight) years to undo the damage and create a favorable and lasting image for himself.

The latest signals from the McCain campaign—one top aide told The Washington Post that they’d “strike a new tone” in the race’s closing weeks—along with last week’s decision to pull resources from Michigan confirm that McCain and his team are well aware that tearing down Obama and making him personally unacceptable to swing voters now represents their best, and likely only, chance of overtaking him.

With a New York Times story as a prompt, McCain deputized Sarah Palin over the weekend to question Obama’s association with Bill Ayers, giving new life—and a much louder voice—to charges that conservative talk show hosts and activists have been leveling against Obama for months. And McCain himself pointedly suggested on the campaign trail late last week that he’d “take the gloves off” starting in the second presidential debate, scheduled for Tuesday night. An aggressive effort to resurrect Jeremiah Wright and all sorts of baseless rumors about Obama’s faith and family—whether orchestrated by the McCain campaign or “independent groups”—now almost seems inevitable.

Maybe it will work, and voters who now generally like Obama (and deeply dislike the Republican Party) will clam up at the last minute, unable in the end to pull the lever for a man that seems so “risky” and unknown. After all, the G.O.P. has played this game before—most successfully in 1988 against Michel Dukakis, but also in 2000 with Al Gore and in 2004 with John Kerry.

But it doesn’t always work. George H. W. Bush’s strategists believed they’d be able to engineer a victory against Clinton in 1992 by using the same techniques they’d used against Dukakis. Clinton had, for all intents and purposes, dodged the Vietnam draft, cheated on his wife and earned a reputation for slippery evasiveness throughout the ’92 campaign. But they got nowhere with this approach, in part because voters in ’92 were focused so intently on their own economic peril (and thus not as swayed by character politics) and in part because Clinton’s sunny personality provided him with an insulation from personal attacks that Dukakis never enjoyed. Bush raised Clinton’s Vietnam draft record briefly in that campaign only to watch it backfire.

As in ’92, economic uncertainty, if not panic, has come to dominate the 2008 campaign. Once again, many voters consider the election too important to be distracted by personality issues, and once again, it is a Republican administration (and the party as a whole) that is taking the most heat. And while Obama doesn’t exude the same empathy that Clinton did, his manner and his story agree with far more voters than not. Most voters instinctively like Obama. The same could not be said of the last two Democratic nominees. This suggests there will be a limit to the effectiveness of whatever personal attacks the McCain campaign is planning.

And that raises the issue of the risk McCain may be taking with his own reputation. If he takes his campaign into the gutter and wins, he would have an opportunity as president to build a record and a legacy that would reduce his ugly campaign to a footnote in his legacy – much the way criticisms of George H. W. Bush’s ’88 campaign don’t play as prominent a role in his legacy as his administration’s accomplishments (and failures).

But Bush was ahead of Dukakis at this point in ’88 by as much as McCain now trails Obama. He could afford to risk his reputation.

If McCain does take the low road and loses next month, he will find reclaiming his reputation almost impossible. It’s not like he’d have another chance at the White House in four years.

Twelve years ago at this time, Dole was urged by Republicans to crank up the attacks on Clinton’s character. But Dole mostly ignored them, instead conducting two exceedingly civil debates with his opponent and offering restrained, nonpersonal attacks on the campaign trail. As a result, he walked away from the ’96 campaign with his reputation enhanced. When it was over, Clinton actually presented him with the Presidential Medal of Freedom, and Dole set off on a second career as a part-time humorist.

But Dole knew he was cooked well before Election Day. The prognosis for McCain is murkier. Just murky enough, it seems, to put a career’s worth of hard-earned respect on the line.