By NBC's Carrie Dann

STORM LAKE, Iowa -- The X-factor candidate in the Iowa caucuses is in Rick Perry's crosshairs. 

"Dr. Paul's just wrong on this issue," Perry said on Friday after ripping his libertarian-leaning rival's view that hawks have inflated the dangers of a nuclear Iran. "You can't make nice with the mullahs. They hate us." 

Perry, who trails Paul in the first caucus state, said that Paul's isolationist policies "truly make me nervous" and warned Iowans at two small-town campaign stops that such views could lead to the destruction of Israel or even the United States. 

"We cannot have a president of the United States that basically is so hands-off to a country like Iran that they say "it's not our business, we're not going to get involved,' he said. "It is our business." 

The swipes come as political observers increasingly wonder if Paul's organizational strength and fervent base of support could vault him to victory in the Jan. 3 caucuses. 

But Team Perry hopes that Paul's dogged doveishness, particularly on the issue of a nuclear Iran, is a bridge too far for Iowans. 

"You're trying to dramatize this, that we have to go and -- and treat Iran like we've treated Iraq and kill a million Iraqis, and 8,000- some Americans have died since we've gone to war. You cannot solve these problems with war," Paul protested during Thursday night's FOX News debate in Sioux City. 

Bob Haus, Perry's Iowa state co-chair, told NBC News after the debate that Paul's comments about Iran could give pause to voters who have been drawn to the congressman's deficit- and spending-based message. 

"His success has really stemmed around the economic side of his message," Haus said of Paul. "And in debates like tonight when you start seeing the foreign policy side of his message, that's where he starts to really have some difficulties. I don't think he represents most Republicans or even most Iowans on a lot of these defense issues." 

• Perry faces questions about retirement pension

Paul was not the only GOP candidate on the receiving end of a jab from Perry during the third day of his Iowa barnstorm. Asked by a reporter if former House Speaker Newt Gingrich's work for Fannie Mae and Freddie Mac disqualified him from serving as president, the Texas governor slammed Gingrich's attempts to distance himself from the label of "lobbyist." 

"The idea that somehow or another 'I'm a consultant, I wasn't a lobbyist.' ... For most of us that is a very weak excuse at best," Perry said. 

Perry hit stops number four and five of his 44-destination Iowa bus tour, appearing in two crowded but intimate venues in conservative northwest Iowa. The retail-rich blitz is designed to repair the damage from Perry's early debate stumbles by placing the candidate face-to-face with Iowans.

But the campaign faced disappointment late Thursday night when it lost a key endorsement race in South Carolina, with Gov. Nikki Haley announcing her backing of Mitt Romney. 

"I respect Nikki. [She's a] good governor," Perry said today. "But, you know, she made her choice. And we'll see who was right."