Democrats are attacking Joni ErnstJoni Kay ErnstAgricultural trade demands investment in MAP and FMD GOP senator: Trump's rhetoric not to blame for North Korea nuclear threat Rep. Sinema to challenge Flake for Senate seat MORE, the front-runner in the Iowa Republican Senate primary, for calling the slayings at the University of California, Santa Barbara an "accident."

Ernst was asked during a debate Thursday night about whether she regretted the timing of a recent ad in which she shoots a handgun.

"No, this unfortunate accident happened after the ad," she said.

"What happened in that shooting and that stabbing is an absolute tragedy; however, I remain firm in my commitment to the Second Amendment," she said. "And again, just because of a horrible, horrible tragedy, I don't believe we should be infringing upon people's Second Amendment rights."

Democrats have been critical of Ernst's ad, in which the National Rifle Association endorsee vows to "take a shot at ObamaCare."

They jumped on the comments.

"She described Santa Barbara as an accident," Jeff Link, a strategist for Democratic Senate candidate Bruce Braley's campaign, said in an email to the Des Moines Register. "This was a rampage against women with knives and guns."

Ernst and her GOP opponents mostly ignored one another and didn't land any blows during the debate, a sign there will be little to shake up the race before next Tuesday's primary. Ernst has built a solid lead in the polls. She's also campaigning later on Friday with former presidential nominee Mitt Romney, the latest big-name Republican to swing through the state to help her bid.