DUBUQUE, Iowa -- Americans already hate politics, and the latest ugly spat between the presidential candidates is likely to sour them even further.

Donna Stehn explained why.

The 57-year-old retired speech pathologist from Peosta, Iowa, already is muting her television when the ads come on. Not all the ads, just those that feature the presidential candidates.

“We’re sick of it,” she said. “All this stuff that they’re saying, it sounds like a junior high school campaign. “

A Democrat who caucused for President Barack Obama in 2008, Stehn attended his campaign rally Wednesday by the banks of the Mississippi River and is enthusiastic about voting for him again. She reserves most of her disdain for what she says are Republican challenger Mitt Romney’s “lies and distortions.”

But she’s also disappointed that Obama chose to engage: He slyly joked in Iowa this week about the infamous incident when Romney drove to Canada on vacation with the family dog in a carrier on the roof of the car.

The Romney campaign, meanwhile, offered its own blasts, suggesting that Obama should take his “campaign of division and anger and hate back to Chicago.”

From incendiary rhetoric, such as that Romney’s plans for Wall Street would put people "in chains," to saying that Obama’s campaign "has disgraced the presidency," the campaign is knocking on the door of being the ugliest in a generation, and the party conventions haven’t even been held yet. It’s unfolding amid claims from both sides that the race will be about substance and big issues.

“Both sides should focus on the positive,” Stehn said. “There’s enough accomplishments. Be bigger and rise above it.”

Given the stakes, that’s unlikely to happen. The latest round of fighting “reinforces the view of a lot of people” that politicians too often are squabbling and not doing what they were elected to do, said Dennis Goldford, a professor of politics at Drake University in Des Moines.

A Gallup survey last month found that 64 percent were thinking quite a lot about the election. But that’s down from comparable 2004 and 2008 levels, Gallup said, and turnout could suffer.

Indeed, one big risk with ratcheting up the rhetoric, experts say, is that the already-alienated segment of the electorate will find fresh reasons to stay home on Election Day. A new Suffolk University-USA Today poll released Wednesday found that about 40 percent of adult Americans don’t plan to vote this fall.

The main reason? People were too busy, or thought that their votes didn’t matter. And majorities said they didn’t pay attention to politics because it was a bunch of empty promises and corrupt.

Both campaigns might want to think about the fallout of their messaging lately. Stehn said she feared that the president’s remarks on the dog controversy could turn off independents. Crowds laughed, but Stehn said, “If you’re a supporter, you roll your eyes and wish he’d stop doing it.”

Harry Tibbetts, 72, an Obama supporter in Dubuque, said the two candidates “are telling outright lies about each other, especially that Romney guy.”

Still, Obama has “got to come back at him,” the retired Reliant Energy worker said. “You fight fire with fire.”