Sen. Lindsey Graham, R-S.C., blasted House Democrats Wednesday for their continued push for impeachment as the House Intelligence Committee prepares to hold public hearings next week.

"The whole thing is being driven by partisans in the House. Adam Schiff is not looking for the truth. And the testimony is incoherent. It depends on who you talk to," Graham said Wednesday on "The Story with Martha MacCallum." "But there is one common theme here, the president of the Ukraine and the president of the United States -- both said there was no quid pro quo."

Democrats on Wednesday released a transcript of testimony from U.S. diplomat Bill Taylor in which he claimed to have a “clear understanding” that President Trump wanted to leverage military aid to Ukraine in return for investigations that could benefit him politically. Taylor did acknowledge he didn't have firsthand knowledge of "what was in the president's mind."

The House Intelligence Committee will hold its first open hearings next week as part of the formal impeachment inquiry into Trump, featuring current and former officials with knowledge of the Ukraine controversy.

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"The most important facts are largely not contested," House Intelligence Committee Chairman Schiff told reporters Wednesday. "The president enlisted whole departments of government in the illicit aim of trying to get Ukraine to dig up dirt on a political opponent, as well as further a conspiracy theory about the 2016 election that he believed would be beneficial to his reelection campaign."

"You know, that statement's full of crap," Graham said in reaction to Schiff's statement. So Bill Taylor ... what does he base his belief that there is a quid pro quo on? What is the factual basis?"

Graham also questioned why E.U. Ambassador Gordon Sondland revised his testimony to describe a quid pro quo, calling it "suspicious."

"Why did Sondland change his testimony? Was there a connection between Sondland and Democratic operatives on the committee? Did he talk to Schiff? Did he tell it to Schiff's staffers?" Graham asked. "I've been a lawyer for a very long time. When somebody changes their testimony, they suddenly recall something they didn't know before. It makes me incredibly, incredibly suspicious."

Tuesday's transcripts revealed Sondland revised his prior testimony to say that he told a top Ukrainian official that U.S. aid would likely not resume until the country issues a corruption statement -- a revelation that was quickly hailed by Democrats of proof of the quid pro quo they have been alleging took place.

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Graham also went after the whistleblower, saying the statute protecting his or her identity was being abused.

"The whistleblower statute is being abused here. It does not give a person anonymity when it comes to making a claim of wrongdoing. It protects them from being fired," Graham said. "The Constitution trumps the statute. No American, including Donald Trump, should be accused of something based on an anonymous source."

Fox News' Brooke Singman contributed to this report.