"You work hard, you’re honest, you could have a good life in America. That’s what I believe. But somehow these politicians in Washington think they can live by a different set of rules. The only way to change Washington is to change the people we send there," he says.

Absenteeism has up until now been an issue mostly highlighted by Brown's campaign, which has pointed out that Mandel himself missed the first 14 meetings of the State Board of Deposit when he took office as State Treasurer in Ohio.

That's not unusual, as treasurers often send surrogates to these meetings, but The Associated Press reported that Mandel was the first treasurer in recent history to miss that many meetings in his first term. Brown's campaign pointed again to this fact in its response to the ad.

The Brown campaign also pointed to GovTrack statistics that showed that, from the beginning of his tenure in Congress, in January of 1993 to September of 2012, he's only missed 3 percent of possible votes, and has made 98 percent or more of his votes each year he's been in Congress, according to Congressional Quarterly.

Though 3 percent seems like a small amount of votes to miss, it's higher than what GovTrack says is the median number of missed votes for most lawmakers — 2.5 percent. Brown's campaign insists he would've missed fewer votes if not for his mother's passing and his recovery from a car accident, and that most others were due to late flights.

Brown remains ahead in most polls, with the two most-recent showing him slightly expanding his lead over Mandel. But Ohio is by no means an easy win for the Democrat; President Obama is only running slightly ahead of Mitt Romney there, and the Democratic Senatorial Campaign Committee recently reserved $2 million in fall airtime for the state to prepare for what's likely to continue to be a fierce battle.

—This post was published at 12:20 p.m. and updated at 2:27 p.m.

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