Republican presidential frontrunner Mitt Romney took aim Friday at chief rival Ron Paul as a fringe candidate in the final four days before the Iowa caucuses, The Associated Press reports.

“I’m working harder than anyone to make sure he’s not the nominee,” said the former Massachusetts governor during a campaign stop in West Des Moines with New Jersey Gov. Chris Christie at his side. “I don’t think Ron Paul represents the mainstream.”

The AP reports that Ron Paul, campaigning on the western side of the state, did not immediately respond.

Romney repeated his attacks on the Texas congressman in interviews with Fox News Channel and NBC News after the appearance with Gov. Christie, as part of a coordinated effort to soften Paul’s momentum ahead of Tuesday’s first-in-the-nation GOP nominating contest.

The latest Iowa NBC/Marist poll released Wednesday shows Romney and Paul in a statistical tie for the lead among likely caucus-goers, 23 to 21 percent. The two are followed by former Pennsylvania senator Rick Santorum at 15 percent, Texas Gov. Rick Perry at 14 percent, former House speaker Newt Gingrich at 13 percent and Minnesota congresswoman Michele Bachmann at the back of the pack at 6 percent.

MSNBC reports that Tea Party supporters – who make up nearly half of all likely caucus-goers – are essentially divided across the Republican field.

Santorum gets 20 percent from Hawkeye State Tea Party supporters, followed by Romney and Paul at 17 percent. Gingrich is in fourth place with 16 percent; Perry earns 15 percent followed by Bachmann with 10 percent.

“This is the Romney dream scenario,” said Lee Miringoff, the director of the Marist College Institute for Public Opinion, which conducted the survey. “When you look at the Tea Party and conservatives, they are all splintered.”

The Iowa NBC-Marist survey was conducted December 27-28 of 2,905 registered voters (margin of error of plus-minus 1.8 percentage points) and of 433 likely GOP caucus-goers (plus-minus 4.7 percentage points).