American Conservative Union Chairman Matt Schlapp said Tuesday that an impeachment investigation of President Trump is a sign of how desperate Democrats are to defeat him in 2020.

“Their only politically viable avenue is scandal, investigation, impeachment with Trump,” Schlapp told “The Daily Briefing with Dana Perino.

“They can’t win on the economy, they can’t win on China, they can’t win on America’s role in the world so they can only win when they pick this scab of scandal,” he said, referring to the Ukraine phone call controversy.

UKRAINE CONTROVERSY TURNS INTO DOUBLE-EDGED SWORD FOR BIDEN

Schlapp made the assessment just hours before Pelosi announced a formal impeachment inquiry, saying "the president must be held accountable" for what she described as Trump's "betrayal of his oath of office, betrayal of our national security, and the betrayal of the integrity of our elections."

Invoking the "darkest days of the American Revolution," Pelosi called on lawmakers to honor their constitutional oath to protect the country "from all enemies, foreign and domestic."

The president said Tuesday that he would release an unredacted transcript of the phone call with Ukrainian President Volodymyr Zelensky.

TRUMP’S UKRAINE CONTROVERSY CAST SPOTLIGHT ON HUNTER BIDEN’S BUSINESS DEALINGS

Administration sources told Fox News that the freeze on Ukrainian aid was tied to concerns about corruption. Those sources said that Trump wanted to be confident that the incoming Zelensky administration was going to take steps to end corruption before releasing the funding.

Sources tell Fox News that the aid was released last month after Sen. Rob Portman, R-Ohio, called Trump and urged him to do so.

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“The American people are going to horsewhip the Democrats for their ridiculous scandal-mongering on things that really don’t deserve this kind of attention,” Schlapp said, referencing the two-year-long Russia investigation which, he claimed, was “a lie in the beginning based on false premises."

Fox News' John Roberts, Brooke Singman contributed to this report.