Former South Carolina Gov. and Trump primary challenger Mark Sanford Mark SanfordOn The Money: Business world braces for blue sweep | Federal Reserve chief to outline plans for inflation, economy | Meadows 'not optimistic' about stalemate on coronavirus deal Trump critic Sanford forms anti-debt advocacy group Republicans officially renominate Trump for president MORE (R) used the famous Wendy’s slogan-turned-political-joke to criticize President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE for not completing the border wall between the U.S. and Mexico, one of the president’s central campaign promises.

“Where’s the beef on that promise, because your wall has not been built over the course of the administration’s last couple years,” Sanford said, while holding a sandwich outside of an Arby’s restaurant near the Iowa State Capitol, according to a video tweeted by Des Moines Register reporter Shelby Fleig.

Currently outside Arby’s near the Iowa State Capitol, @MarkSanford is using a roast beef sandwich as a prop to ask “Where’s the beef?” re: Trump policy promises #iacaucus pic.twitter.com/VZYKfn7dpE — Shelby Fleig (@shelbyfleig) September 25, 2019

“Where’s the beef” was a tagline used in a Wendy’s commercial in the 1980s. The phrase then entered politics when Democratic presidential candidate Walter Mondale used the line against Sen. Gary Hart during the 1984 Democratic primary while criticizing his policies.

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Sanford announced earlier this month that he would be challenging Trump in the 2020 GOP primary. He has said his campaign is about improving the ideas of the Republican Party.

"There's a robust debate going on on the Democratic side about what it means to be a Democrat. There ought to be an equally robust debate on the Republican side on what it means to be a Republican," Sanford said in an interview with MSNBC earlier this month.

"This is about improving the ideas that the Republican Party stands for," Sanford added. "Some people say, 'No, this could hurt his chances.' I say it could make him better."