Brian Brown, the president of the National Organization for Marriage (NOM), claims in a blog post that Republican presidential candidate Donald Trump has “abandoned the fight to preserve marriage as the union of one man and one woman.”

The nation's largest group dedicated to undermining the Supreme Court's finding that gay and lesbian couples have a constitutional right to marry endorsed Senator Ted Cruz's presidential ambitions late last year.

(Related: Brian Brown: NOM endorsement helped Ted Cruz surge.)

On Thursday, just four days before Iowans kick off the process of picking the next president of the United States, Brown claimed that Trump is merely pandering on the issue and crowned Cruz “a champion for marriage.”

“The controvertible record demonstrates that Ted Cruz will be a champion for marriage while Donald Trump has abandoned the fight to preserve marriage as the union of one man and one woman,” Brown wrote. “It’s just as simple as that. It’s very easy for skilled politicians to create an impression on the stump that they are with you and agree with your values and position on key issues. For example, pretty much every Republican candidate for president will say that they believe marriage is the union of one man and one woman.”

“But that is a meaningless statement given where we are in the wake of the US Supreme Court’s decree imposing same-sex ‘marriage’ on the nation. Saying is one thing; doing is another. The real question is what will the various candidates actually do to fight to restore marriage to our laws and protect the right of people to continue to act in concert with their belief that marriage is only one man and one woman?”

“That is why NOM developed our Presidential Marriage Pledge and fashioned it along the lines of specific actions a candidate will take if elected president. And in the ‘doing’ department, Ted Cruz is light years better for us than is Donald Trump.”

During an appearance earlier this month on ABC's This Week, Trump called Cruz a “hypocrite” on the issue: “Just so you know, he's taking money from people who are very much into the whole gay marriage situation and he's taking money from them and, you know, raising funds from them … He's a total hypocrite.”

Trump was referring to comments Cruz made at a Manhattan fundraiser, where he said that “fighting gay marriage” would not be a “top-three priority” in his administration.

(Related: At Manhattan fundraiser, Ted Cruz says opposition to gay marriage not a priority.)