Campaign ads go negative in Iowa as Romney, Gingrich, Ron Paul mix it up (VIDEO)

Campaign ads bombard Iowa, as the Republican candidates and their surrogates step up efforts to raise doubts among caucus-goers about their rivals. In some ads, that means going negative.

Mitt Romney doesn't like Newt Gingrich. Ron Paul doesn't like Mitt Romney. And Mr. Gingrich has little love for either one of them.

At least that's the impression coming through from TV ads and candidates' responses, as the clock ticks closer to the Jan. 3 Iowa caucuses. 

Some of the ads are positive. Some go after the candidate of the opposing party, President Obama. But as the race for Iowa draws to a finish, with no clear winner in view, the campaigners have stepped up efforts to raise voter doubts about their rivals for the Republican nomination.

Some of the mud-slinging is being done by surrogates, the so-called "super PACs" (political action committees) that can draw unlimited amounts of money from donors.

A super PAC working on Mr. Romney's behalf, Restore Our Future, is airing ads that say former House Speaker Gingrich has "too much baggage" to beat Mr. Obama. Romney and his allies have oodles of money to spend on the effort.

In response, a Gingrich-supporting group is broadcasting spots that say Republicans are "attacking him with falsehoods," and Gingrich has personally urged Romney to be "man enough" to rein in his super PAC supporters.

The pro-Gingrich group, Winning Our Future, warns Iowans not to let "the liberal Republican establishment pick our candidate."

Haven't heard of the "liberal Republican establishment" before? From the context, it seems safe to say the ad means Romney backers who come from the corporate world and who aren't perceived as pure conservatives on issues such as abortion, gun rights, or a balanced budget amendment to the Constitution.

For his part, Romney has said campaigns are partly in the business of drawing distinctions among candidates. He has wondered aloud if Gingrich can "handle the heat in this little kitchen," which will only get hotter in a general-election campaign.

Rep. Ron Paul of Texas has mounted attacks of his own, which could grow louder on the airwaves as he sets his sights on a potential first-place finish in Iowa.

"Serial hypocrites [photo of Gingrich] and flip-floppers [photo of Romney] can't clean up the mess" in Washington, says a new ad from the Paul campaign. It then touts Congressman Paul's budget-balancing plan and calls him "the one we've been looking for."

The opening of the Paul ad has the look of a movie trailer – no accident, as campaigns struggle to grab voters' attention and get them to turn out for the Jan. 3 caucuses.

In fact, a sibling commercial by the Paul campaign actually opens with a green screen showing the words "the following preview has been approved for all audiences." (A story "of smooth-talking politicians" and a ready-to-conquer hero follows.)

Some recent polls in the state show Paul, Romney, and Gingrich as the leaders in a six-candidate field. (Another Republican aspirant, former Utah Gov. Jon Hunstman Jr., is not campaigning in Iowa.) Texas Gov. Rick Perry, Minnesota Rep. Michele Bachmann, and former Pennsylvania Sen. Rick Santorum aren't out of the running, given that even a third-place finish in Iowa can bring a candidate some momentum to compete in subsequent primary votes.

Indeed, Mr. Santorum has edged ahead of Gingrich in the latest poll, with 16 percent of likely attendees at the Iowa GOP caucuses. Romney had 25 percent and Paul 22 percent in the CNN/Time/ORC poll.

The candidates also seek to woo Iowans with positive pitches.

One new Romney ad plugs his experience at balancing budgets, saying that it's a "moral imperative for America to stop spending more money than we take in. It's killing jobs...."

The Ron Paul ads segue seamlessly from the problem (the other guys in Washington) to promotion of Paul and his ideas as the solution.

Gingrich is the self-avowed Mr. Sunshine of the campaign, with a recent pledge to stay "relentlessly positive." 

His recent digs against Romney (a "Massachusetts moderate") and Paul ("totally outside the mainstream") make that upbeat image harder to sustain. But his TV ads echo the "morning in America" themes used so effectively by Ronald Reagan.

One new Gingrich ad called "Winning the Argument" uses debate footage showing some of his rivals nodding approvingly as he sings the praise of free markets. Another new spot has the candidate intoning: "If you hear high unemployment is our new normal, just say boloney! We can create millions of jobs right now."