URBANDALE, Iowa

Newt Gingrich had been attacked one too many times by the Romney campaign this week. At the opening of his Urbandale office today, Gingrich chastised the Romney campaign for negative advertising. But never mentioned Romney's name.

"I'm happy to compare records. But what we will not do, we won't engage in negative ads and we won't engage in tearing people down," Gingrich said.

Mitt Romney's campaign released a series of attacks against Gingrich this week. The first came in the form of the ever-popular email, titled, "With Friends Like Newt, Who Needs the Left?" The email was followed by a conference call with Romney surrogates who called Gingrich "self-aggrandizing" and "anti-conservative," among other things.

Gingrich used President Obama as the main reason the Republican candidates should not attack each other.

"I've got good friends who are running. Everyone of them I believe would be better than Barack Obama," Gingrich said. "We should have a positive campaign on the Republican side so that whoever comes out of this is strong enough to defeat Obama."

Gingrich laid out his campaign strategy several months ago, telling ABC News, "You will not hear me say a negative thing about the other candidates." Since then, Gingrich overall has stayed above the fray, but did call out Romney on CNN last week, saying he was "stubborn" for backing his health care policies in Massachusetts. He also said he was "a lot more conservative than Mitt Romney," last month to the Charleston, S.C. AM News.

"I'll tell none of my surrogates are going to be encouraged to go out and attack anyone," Gingrich said. "We have lots of good, positive things to talk about."

Tonight Gingrich will be in the ABC News debate, where he will likely endure more attacks from the other candidates as he leads S.C., Iowa and Florida in national polls.