McCann, who is an elected Democratic state representative, is not alone in her dislike for negative advertising. At the party's national convention in Charlotte last week, many delegates were concerned about the tone of both sides' campaigns.
"I actually think people are getting really sick of it," McCann said. "What I'm most worried about is that people in Colorado will say: 'We've had enough of this, we're not voting. We're sick of it, we're not going to vote.'"
Since then, however, Barack Obama has joined the fray, regularly running negative spots including an ad which features a rather off-key Romney singing 'America the Beautiful' while critical quotes from news reports pop up on screen.
"It's really unfortunate that the tone of the campaign has been very negative. I really don't think that negativity in campaigning has any place," said Ned Norris Jr, a delegate for Arizona. "It's not productive. It's anti-productive. And when we think about the negative campaigning that's going on we have to be concerned about what others see in that negativity. I think negativity campaigning just fuels negativity that's already going on throughout the United States."
The overriding sense among delegates that this election cycle has largely been conducted in the gutter is supported by the data. In January, the Campaign Media Analysis Group, which studies election advertising, declared the Florida primary to be "the most negative campaign ever" , after finding that 92% of ads aired in the state during the final week of the Republican primary were negative in tone.
Bill Benoit, professor of communication studies at Ohio University, had similar, if not quite as dramatic findings after conducting a wider study of the tone of adverts used across all the primaries.
Benoit compared some 90 adverts run by Republican candidates across various states during the primaries to a database of ads run by politicians dating back to 1952. He added up all the statements in advertisements run by Republican primary candidates and found that 55% were negative, compared to an average of only 25% in ads run between 1952 and 2012.
Benoit will conduct a study of Obama and Romney's advertising after the presidential election on 6 November, and he has a good idea what he will find.
"I think as a whole 2012 will be remembered as one of the most negative campaigns ever if not the most negative campaign ever," he said. "There has always been incivility but it seems to me the partisan hostility has been even higher. It's just degenerated into a vicious vilification of everything the other party stands for."
Florida was particularly hard hit in January, as Romney and Gingrich slugged it out in the primary. Voters in the crucial swing state have been targeted again this summer.
"We have all these TV ads, all these mailers, just kind of flooding the markets with this really dirty messaging that they can do," said Amy Ritter, a Democratic delegate from Orlando, Florida. "It's made it much more difficult for the true message to come out because at the end of the day you want to hear what the candidates are going to bring, what they're standing for, not just slinging mud and digging in the dirt looking for ways to attack the other party."
Ritter laid the blame squarely with the rise of Super PACs after the Citizens United v Federal Election Commission ruling in 2010, which said there should be no limit to the amount of money corporations can spend on advertising, as long as that money remains independent of candidates. It was a common criticism among delegates.
"Campaigning has got very negative because of all the big money that's there. It's uncontrolled," said Larry Capp, a Democratic delegate from Miami, Florida, who called for campaign-finance reform. "We need to have spending limits on how much these private organisations can put into campaigns."
However, even as Super PACs and candidates pump out more and more negative ads, there is no hard evidence that such advertising works.
"The research clearly shows that negative ads are not more persuasive than positive ads," Benoit said.
Stephen Craig, professor of political science at the University of Florida, said: "A lot of people have done research on this. Some studies show that negative attacks work, others show that they don't and there's really no bottom line.
"On balance, it's that they work some of the time, and that's the big catch in all of this."
Both Benoit and Craig said that the tone of advertising may be dictated by "anecdotal" evidence, which is relied upon among political strategists.
Craig said: "Everyone remembers the races where a negative attack or series of attacks appears to have been decisive. That's the kind of knowledge candidates and consultants have – it's anecdotal evidence. The scholarly evidence doesn't back them up.
"Here's the deal – why are there so many negative ads? Because candidates and consultants believe they work.
"It really isn't the negativity that's effective. It's the message. Some messages are more effective than others, some messages resonate more than others. If you've got a powerful negative message that resonates with voters, then yeah, it's going to work. But if it's about something voters don't care about, if it's a message that's poorly presented, then they're not going to be moved by it.
"Can it work? Yes. Does it work? Sometimes."
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