JOHNSTON, Iowa — Iowa conservative leader Bob Vander Plaats called on Rep. Michele Bachmann to drop out of the Republican race and for Newt Gingrich and Rick Perry to reassess their campaigns following expected lackluster performances in the Iowa Caucuses.

Vander Plaats, whose influential organization, the Iowa Family Leader, did not endorse a candidate, threw his weight behind Santorum last month after approaching both him and Bachmann about quitting the race and endorsing the other.

“The worst thing that can happen to Mitt Romney is to run head to head against Rick Santorum,” he told reporters at Santorum’s campaign headquarters here tonight. “He wants to have a multiple candidate field, so I think some of these candidates — they need to reassess where they are at tonight.”

“I think Michele Bachmann has to definitely [drop out],” he added.

Vander Plaats said he is reaching out to social conservatives and pro-life leaders in New Hampshire, South Carolina, and Florida to throw their weight behind Santorum in the coming days.

“We did this drill four years ago. Had Fred Thompson not stayed in the race in South Carolina and takes nine percentage points, Huckabee wins South Carolina,” he said.

“If Huckabee wins South Carolina, McCain is out of the race and it’s Huckabee-Romney going into Florida. So what I’m saying is that we have to be smart about getting a pro-family conservative to go up against Mitt Romney.”