GOP senator: Trump has changed presidency 'not necessarily toward the positive'

Johnson added that former President Clinton had also shifted the "behavior and the standard of the presidency."
"It's unfortunate. I revere our Constitution. I revere these institutions, including the office of the presidency. It would be nice if everybody conducted themselves, I guess, the way we would here in Wisconsin," Johnson continued. 
Johnson was asked about Trump's behavior, but didn't point to a specific incident during the interview. His comments come as Congress is locked in an impeachment fight fueled by the president's interactions with the leader of Ukraine.
Johnson, who has emerged as one of Trump's most vocal supporters on Ukraine, said on Monday that "there has been a concerted effort from Day 1 to sabotage this administration." 
"I don't agree with everything he's doing, but I have to give him a great deal of credit," Johnson said. 
The White House last week released a partial transcript of Trump's call with Ukrainian President Volodymyr Zelensky. In the call, according to the document, Trump asked Zelensky to work with his personal attorney Rudy GiulianiRudy GiulianiArizona certifies Biden's victory over Trump Krebs says allegations of foreign interference in 2020 election 'farcical'  Trump campaign loses appeal over Pennsylvania race MORE, and expressed hope that he “can look into” former Vice President Joe BidenJoe BidenGeraldo Rivera on Trump sowing election result doubts: 'Enough is enough now' Senate approves two energy regulators, completing panel Murkowski: Trump should concede White House race MORE and his son.
Johnson said on Monday that there was no "quid pro quo" in the Trump call, but that he has "a lot of questions" about Ukraine and Democrats. 
"Everybody says well there's no evidence, all these things have been debunked. ... [But] I have all kinds of questions dating back to Hillary ClintonHillary Diane Rodham ClintonBiden budget pick sparks battle with GOP Senate Katko fends off Democratic opponent in New York race Harris County GOP chairman who made racist Facebook post resigns MORE's email scandal," Johnson said. 
Johnson and Sen. Chuck GrassleyCharles (Chuck) Ernest GrassleySenate GOP open to confirming Yellen to be Biden's Treasury secretary Biden budget pick sparks battle with GOP Senate Grassley returns to Capitol after having coronavirus MORE (R-Iowa) sent a letter late last week to the Justice Department asking for an investigation into any ties between Hillary Clinton and Ukraine. 
Johnson has also called for an investigation into Biden, including suggesting that a Senate investigation would be "completely appropriate."