Groups focused on stopping Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE from becoming the GOP's presidential nominee will begin airing ads Thursday aimed at unbinding delegates at the Republican National Convention.

The first ad, which will air on WHO-AM radio in Des Moines, Iowa, is focused on Steve Scheffler, a member of the Republican National Committee, The Wall Street Journal reported. The ad is funded by the Courageous Conservatives PAC and urges people to contact Scheffler, one of Iowa's two representatives on the Rules Committee. The PAC is run by Steve Lonegan, who formerly served as the New Jersey state chairman for Ted Cruz Rafael (Ted) Edward CruzVideo of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Democrat on Graham video urging people to 'use my words against me': 'Done' MORE's presidential campaign.

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The ad criticizes Scheffler for trying to "force Republican delegates to vote for Donald Trump and threatening those who find that vote to be morally offensive."

The ad says delegates have the role of making decisions in the best interest of the party and its conservative values.

"Normally, our delegates would ratify the primary winner. But this is one of those times when the delegates need to be free to vote their conscience," the ad says.

It then urges people to call Scheffler to push him to let delegates pick the "best Republican to fight for our conservative values and beat Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE."

Scheffler slammed the effort, calling it a "slap in the face of conservative activists in 50 states and six territories who have spoken," The Wall Street Journal reported.

“These people spent all of their time trying to destroy people and they don’t do anything productive,” Scheffler told the WSJ. “Nothing, zero. What is the end result? You want to have a big war so somebody else is the nominee when the enemy is Hillary Clinton.”

He also said he won't be intimidated by people involved in the effort to unbind delegates.

“These people are a bunch of bullies," he said. "I’m not going to go against the will of the people from across this country."

Other ads set to air on national cable TV this weekend are run by a group looking to press delegates to say they are unbound even if it goes against convention rules.

"The voters don't decide who the nominee is, the delegates do," said Eric O'Keefe, who is organizing another group aimed at stopping Trump.