Former President Bill Clinton and President Obama used to have a famously rocky relationship. But the days when Clinton tried to help his wife, now secretary of state, defeat Obama in the 2008 primaries are ancient history.

Former Clinton strategist Carter Eskew says the ex-president is almost always an asset for Obama.

"Bill Clinton can do a lot of things for Barack Obama," Eskew says. "He can raise a lot of money. He has very good political instincts and good political ideas. And in an interesting way, Bill Clinton may be able to carry the positive narrative for Barack Obama better than Obama can."

As Obama tries to explain his economic plan to cut the deficit while investing in clean energy, education and infrastructure, he can look to the script Clinton wrote in the 1990s. And Clinton, as a former commander in chief, can help in other ways. He appeared in the first Obama re-election campaign ad — describing the risk Obama took when he ordered the raid that killed Osama bin Laden.

And the former president can skewer Republican challenger Mitt Romney. In this example, Clinton was speaking at a fiscal policy summit: "It's like Romney said, 'I'm running for the president of the student body of this extreme right-wing group, and the real argument was that I couldn't be their president because I wasn't right wing enough, so I had to get over there and pretend that I was.' "

Clinton's point was that it's hard to know who Romney really is.

But sometimes Obama's No. 1 surrogate messes up the talking points. Like the other day on CNN, when Clinton undercut the Obama campaign's attacks on Romney's record as a businessman and a governor.

"There's no question that, in terms of getting up, going to the office and basically performing the essential functions of the office, a man who's been governor and had a sterling business career crosses the qualification threshold," Clinton said.

It would be hard to keep the active and voluble former president off the political scene, and for better or worse, he has become the president's highest-profile advocate. But what's more surprising is that he has been given a role in Romney's stump speech.

In Des Moines, Iowa, recently, Romney reminded voters that almost a generation ago, Clinton announced that the era of "Big Government" was over.

"President Clinton was signaling to his own party that Democrats should no longer try to govern by proposing a new program for every problem," Romney said. "President Obama tucked away the Clinton doctrine in his large drawer of discarded ideas, along with transparency and bipartisanship."

After the laughter subsided, Romney went on, "It's enough to make you wonder if maybe it was a personal beef with the Clintons, but probably it runs much deeper than that."

Was Romney trying to revive the feud between the Obamas and the Clintons? That seems unlikely. Instead, says Republican strategist Keith Appell, Romney is trying to target Clinton fans — rural, white, working-class voters in swing states.

"The Romney campaign sees an opportunity to get those people in his column, and not only in states like West Virginia, which is probably going to go for Romney anyway, but people across the border in Ohio and in Pennsylvania," Appell says. "A lot of those folks are Hillary Clinton supporters and fans of Bill Clinton, and they're up for grabs."

Those voters, says Appell, remember that under Clinton, budgets got balanced and welfare was ended — the kinds of positive economic news they're not seeing under Obama.

But former Clinton adviser Paul Begala says that tactic could backfire on Romney.

"All he's doing is setting himself up for a fall," Begala says. "So he goes to, say, southern Ohio, critical swing area, pretty Republican area but the kind of place where President Clinton is very popular, even though it's a pretty Republican area, and he says things like that — well, then Bill Clinton can come in and he'll have the last word."

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