Image Credit: Brendan Smialowski/AFP/Getty Images

In the intense closing hours of this hard fought campaign, with polls so tight in key battleground states, campaigns are looking for any edge, any opportunity to highlight an opponents' foibles.

Case in point: At Springfield High School in Ohio Friday, President Obama made a comment that his opponents have seized upon to paint him as divisive and negative.

Heralding the presidency of Bill Clinton, President Obama said "his economic plan asked the wealthiest Americans to pay a little bit more so we could continue to invest in our people, continue to invest in ideas and innovation, invest in our infrastructure. And at the time the Republican Congress and a Senate candidate by the name of Mitt Romney - "

The audience of around 2,800 booed.

"No, no, no - don't boo; vote!" the president said, as he does at nearly every rally. "Vote!"

Then he added: "Voting is the best revenge."

In West Chester, Ohio, a few hours later, Mitt Romney asked a crowd of more than 20,000, "Did you see what President Obama said today? He asked his supporters to vote for revenge. For revenge. Instead I ask the American people to vote for love of country."

By Saturday morning, the Romney campaign had produced a TV ad with that same theme, titled " Revenge or Love of Country?" and in Marietta, Ohio, Romney running mater Paul Ryan harped on the same theme to a crowd of roughly 1,000.

"Just yesterday he was asking his supporters at a rally to vote out of revenge," said the Wisconsin congressman. "Mitt Romney and I are asking you to vote out of love of country. That's what we do in this country. We don't believe in revenge."

Asked about the revenge kerfuffle, Obama campaign spokeswoman Jen Psaki said, "Mitt Romney is ending this campaign with scare tactics in Ohio with a fake ad about the auto industry," she said, referring to an ad assailed by automakers as false, one suggesting that Jeep jobs in the U.S. are being sent to China. "The President was simply suggesting if you think the American people deserve better and if you believe the President is offering a better deal for the middle class you have the power to cast your vote."

-Jake Tapper and Mary Bruce