The former president carries a full slate of campaign appearances, helps set strategy, and commands the media's attention with every utterance. Or perhaps the more apt analogy, as Clinton stumps vigorously for his wife, Sen. Hillary Rodham Clinton, is that he's running for vice president, a job that often entails going negative.
For more than two weeks, Bill has been playing the bad cop to Hillary's good cop, aggressively going after her top opponent for the Democratic nomination, Sen. Barack Obama, on his record, his assertions, and his experience. By the time Monday's debate rolled around in Myrtle Beach, S.C., the tensions burst into the open.
"I can't tell who I'm running against sometimes," Senator Obama retorted in apparent exasperation over being double-teamed by the Clintons.
On the eve of crucial primaries that could determine who wins the Democratic nomination, a big question looms: Is the outsize role former President Clinton is playing in his wife's presidential campaign a smart strategy?
For now, political analysts are not willing to bet against the Clintons, smart tacticians who clawed back from the brink of political extinction in 1992 and won an improbable presidential victory.
But now that the klieg lights are on – and top Democrats, both black and white, are beginning to issue warnings in the media – the Clintons are on notice not to go too far. Given the racial dimension of their battle, going after the first viable black presidential candidate in history, they are on dangerous turf. African-Americans represent a critical piece of the Democratic coalition, and if Senator Clinton is the nominee, she will need them to turn out for her in November.
"The Clinton people need to blink hard twice and think about this," says Cal Jillson, a political scientist at Southern Methodist University in Dallas. "My sense is that Bill has been an asset, but people are watching him very closely now, and reservations are building."
Still, Mr. Jillson adds, "Bill Clinton is a very sophisticated player and he knows he's near the line and that if he goes over the line it could cause real problems."
So far, the Clinton team has concluded, the former president’s presence on his wife’s campaign has been a plus. And since he began ramping up his rhetoric, she won in New Hampshire and Nevada. In the New Hampshire primary exit poll, 83 percent of Democratic voters had a positive view of former President Clinton, and among that group, Senator Clinton beat Obama by 10 points (while in the overall vote, she beat Obama by just 2 points).
Ultimately though, the Clintons are in uncharted territory. Never before has a former president's wife made a serious run for the Oval Office herself, and so there is no precedent for an ex-president playing such an integral part in a presidential campaign not his own. For Bill Clinton, the rough and tumble of a campaign doesn't square with his post-presidential image as a global figure, doing good works with the first President Bush.
Hillary Clinton is also mindful of her image as a feminist, seeking to become the first woman president. But even as she relies heavily on her husband, she insists she is running "as an individual." At a press conference Tuesday, she was asked if she was trying to belittle Obama subtly in her approach to him as a black man. She said no.
"I think that this is totally about us as individuals," she said. "He is African-American. I am a woman."
But clearly, the Clinton campaign is more an "us" venture than an individual one. Later in the press conference, when asked if she was conceding Saturday's South Carolina Democratic primary to Obama, as she headed off to campaign in other states for a few days, she said she was not. Her husband and her daughter, Chelsea, were staying behind to keep campaigning, she said. Of course, the other candidates have surrogates on the trail, too – spouses, children, celebrities – but none is in the category of Bill Clinton and they rarely go on the attack.
Stopping for a breakfast of fried eggs and grits at a restaurant in Columbia, he defended his role in his wife's campaign and urged the media to move on to other stories.
"I'm a good surrogate for her because except for Chelsea, you know, we know her better than anyone else personally, and we're probably more familiar with her positions," he told reporters. "I don't think it's like her being here, but it's probably the next best thing."
When a reporter asked whether he was playing "attack dog" for his wife, he seemed eager to change the subject, saying voters care more about real issues like the economy and the Iraq war.
Diners at the restaurant applauded when Clinton, in a gray suit and shimmering orange tie, strode in with his security detail Tuesday morning.
"You the man," said one man, handing him a baseball to sign.
"Your wife was spectacular last night," said another, reaching to shake his hand.
But some South Carolinians interviewed this week said their fondness for Bill Clinton didn't translate into support for his wife. "I was once for Hillary Clinton, but then I realized it wasn't for the right reasons – it was for her husband," Kenneth Owens, a paramedic, said Monday after hearing the top three Democratic contenders speak at a Martin Luther King Jr. Day rally at the State House in Columbia.
He said he has since shifted to Obama. "He's African-American and he's trying to offer change," Mr. Owens said.