Yucca Mountain has been a controversial issue in Nevada for years, and it took on added urgency in June when the Bush administration filed a formal application for a construction license to build a nuclear waste dump.
The Obama ad highlights McCain's support of storing nuclear waste in at Yucca Mountain and accuses the Republican of not being "worried about nuclear waste in our state, only in Arizona."
It then shows a 2007 TV interview in which McCain was asked if he'd be comfortable with nuclear waste coming through Arizona.
"No, I would not," McCain says.
Watch the ad below: