Rep. Steve KingSteven (Steve) Arnold KingGOP must now reject Trump’s demands on immigration WATCH: Steve King predicts next immigration wave will come from East Africa Don't get your medical advice from personal injury attorneys' ads MORE (R-Iowa) said Monday that Donald TrumpDonald John TrumpKoch-backed group launches six-figure ad buy against Heitkamp Anti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight MORE won Sarah Palin’s presidential endorsement with his vast “assets and resources.”

“There aren’t very many people who have been able to say no to Donald Trump,” he told MSNBC’s Chris Jansing.

“[It is] not only the plus-ups of the promotion, the limelight,” continued King, the national co-chairman for Ted Cruz’s Republican Oval Office bid.

“He has a massive amount of assets and resources that he can deploy when it comes time to convince someone. That has to impact how people think.”

King argued that Trump's advantages swayed Palin even though she shares more common ground with Cruz.

“I would say that knowing what I know, you never really get down to the heart of hearts. [But] when I see where Sarah Palin has been on policies and issues, I am confident that she is much more comfortable on the issues with Ted Cruz that she is with Donald Trump.”

King added that Iowa’s caucuses later Monday evening are a two-horse race between Cruz and Trump.

“I’ve been saying to voters for several days now that it’s become a binary choice,” he said.

“If you want a constitutional conservative, you vote for Ted Cruz. If you vote for someone else along in that list, because of where they are in the polls it is a de facto vote for Trump.”

Trump leads Cruz by nearly 5 points in Iowa, according to the latest RealClearPolitics average of polls there.

Palin endorsed Trump last month, giving the outspoken billionaire his most high-profile endorsement so far.

The former Alaska governor’s decision was a major blow to Cruz’s campaign given the pair’s past relationship. Palin endorsed Cruz during his 2012 bid for a Texas Senate seat.