The two candidates and outside groups have flooded the airwaves in liberal Denver and conservative Grand Junction and Colorado Springs with tens of thousands of mostly negative ads.
Nationwide, more than 1 million presidential ads have been broadcast since June 1, topping the 2008 ad total by 39 percent and the 2004 total by 41 percent, according to Wesleyan Media Project, an effort by the Connecticut-based Wesleyan University to track political ads.
Anti-Romney ads have been seen more often in the Democratic stronghold of Denver and anti-Obama ads have been more common in Grand Junction and Colorado Springs, which are predominantly GOP areas.
"The river of ads -- the incredible volume of ads -- probably reinforces the preexisting leanings of those who are already comfortably in either Obama or the Romney camp," John Straayer, a Colorado State University political scientist, said Monday. "I also think that we've had so many of them that I question the impact after a while."
The Obama campaign and independent Democratic groups held the early ad advantage by going up on the air as early as the summer to attack Romney.
But Republican groups have stepped up their on-air presence in the final weeks of the campaign and those ads may have given Romney the extra firepower to stay competitive in the tossup state, experts say.
From Oct. 22-29, Obama and his Democratic allies aired their ads a total of 4,610 times in Denver, Colorado Springs and Grand Junction, according to Wesleyan Media Project, which analyzed figures compiled by Kantar Media/CMAG.
Ads by Romney and the GOP camp were broadcast 4,493 times in that week, giving the Democrats an 117-ad advantage, the figures show.
In contrast, Democratic ads were seen 2,827 more times than GOP ones from Sept. 9-30, mostly in Denver, which hosted the first presidential debate that Romney is seen as having won handily.
Across Colorado, independent GOP groups are spending more and putting up more ads than their Democratic counterparts.
That shows Romney is benefiting more than Obama from the 2010 Supreme Court ruling that allowed so-called "super" political action committees to raise and spend unlimited amounts to influence elections.
From Oct. 22-29, Democratic groups broadcast 730 ads in Denver, none in Grand Junction and 226 in Colorado Springs, according to the Wesleyan Media Project. In contrast, GOP organizations took out 1,270 ads in Denver, 282 in Grand Junction and 459 in Colorado Springs.
Peter Hanson, a University of Denver political scientist, said ads won't alter public opinion as long as each candidate put up roughly the same number.
"If one candidate has a significant advantage in advertising, that can move the polls temporarily in their direction," he said. "Generally speaking, the persuasive effect of ads tends to wear off within a short period of time."
Polling data bears that out in Colorado.
Obama's statewide lead was greater when more anti-Romney ads were being shown.
On Sept. 30, the president led by 2.9 percentage points, according to an average of Colorado polls by the web site RealClearPolitics. But by Oct. 30, after GOP ads were being shown almost as frequently as Democratic ones, Romney and Obama were tied.
On Nov. 3, after winning bipartisan praise for his performance in the aftermath of Hurricane Sandy, Obama had opened up a small lead of 0.6 of a percentage point.
Colorado is still considered a tossup that could decide the presidency, though some prognosticators like University of Virginia political scientist Larry Sabato now say Obama will win the state by a hair.
The Federal Election Commission does not require independent groups to report expenditures by state for the general election, making it hard to say just how much outside money is pouring into Colorado to support Obama and Romney.
However, data compiled by the Sunlight Foundation show GOP groups outspending Democratic organizations by a 2-to-1 margin nationwide.
Six of 10 super PACs spending the most money are GOP groups: Restore our Future, American Crossroads, FreedomWorks For America, Winning our Future, Club for Growth Action and Ending Spending Action Fund.
As of mid-October, these groups had spent a combined $308.5 million across the U.S. on presidential and congressional races, a lot of it on negative ads, according to Sunlight Foundation data.
The four Democratic super PACs -- Priorities USA Action, Majority PAC, House Majority PAC and Service International Employees Union PEA-Federal -- had spent a total of $149.6 million.
The Obama campaign has raised more money from a greater number of donors across Colorado and the rest of the U.S. than the Romney campaign.
Without GOP super PAC support, Romney could be behind in the money race and in the polls, said Daniel Newman, president and co-founder of MapLight, a nonpartisan California group that tracks money in politics.
"Given that the resources of super PACs favoring Romney and the Republicans are much greater than those favoring Obama and Democrats â€¦ (it) has helped Romney remain competitive in fundraising and remain competitive in the polls," he said.
Though some experts attribute rising voter polarization to the barrage of negative ads, Newman said the fact is the ads are here to stay because they work.
"I don't think there's any doubt that advertising moves public sentiments," he said. "You wouldn't see hundreds of millions of dollars invested by the campaigns if they didn't."
Written by: Raju Chebium
(Copyright © 2012 USA TODAY)