Sen. Lamar Alexander (R-Tenn.) on Sunday defended his key vote to block witnesses from being called in the impeachment trial, saying President Donald Trump’s dealings with Ukraine were “wrong” but not impeachable.

The Tennessee lawmaker told NBC News’ “Meet the Press” that he will vote on Wednesday to acquit Trump, despite the president’s “inappropriate” actions and his “mistake” of echoing Russian talking points to Ukraine’s president.

“I think he shouldn’t have done it,” Alexander said of Trump conditioning U.S. military aid on Ukraine investigating political rival Joe Biden. “I think it was wrong. Inappropriate was the way I’d say ― improper, crossing the line.”

Alexander, who is retiring instead of seeking reelection this year, said he believes Trump’s actions were “a long way from treason, bribery, high crimes and misdemeanors” and that American voters should decide Trump’s fate in the 2020 election.

He said Trump, if he was truly concerned about Biden, should have asked Attorney General William Barr ― not Ukraine ― to look into the matter.

WATCH: @SenAlexander says “maybe [Trump] did not know how to” call the AG to look into Bidens and Burisma. #MTP@chucktodd: “At what point is he no longer new to this?



Sen. Alexander: “Well, the bottom line, it's not an excuse.” pic.twitter.com/CtZjdB8Cwj — Meet the Press (@MeetThePress) February 2, 2020

Asked why he believes Trump didn’t go to Barr, Alexander said Trump “maybe didn’t know how to do it.”

“At what point, though, is he no longer new to this?” host Chuck Todd asked, noting that Republicans often defend Trump’s controversial actions by saying he’s a political outsider.

“Well, the bottom line, it’s not an excuse,” Alexander said. “He shouldn’t have done it. And I said he shouldn’t have done it.”

Todd then asked whether he’s concerned that the Senate likely acquitting Trump could encourage the president to continue seeking foreign interference.

“I don’t think so,” Alexander said. “I hope not. I mean, enduring an impeachment is something that nobody should like. Even the president said he didn’t want that on his resume. I don’t blame him. So if a call like that gets you an impeachment, I would think he would think twice before he did it again.”

WATCH: @SenAlexander says he hope Pres. Trump does not continue to engage in foreign interference. #MTP #IfItsSunday



Sen. Alexander: “If a call like this gets you an impeachment, I would think he would think twice before he did it again.” pic.twitter.com/gupWRsbEmI — Meet the Press (@MeetThePress) February 2, 2020

Todd also questioned Alexander about Trump’s peddling of Russian propaganda during his infamous July 25 phone call with Ukrainian President Volodymyr Zelensky. Trump had mentioned a debunked conspiracy theory pushed by the Kremlin that alleges Ukraine interfered in the 2016 election. The U.S. intelligence community has repeatedly rejected the claim.

“Does it bother you that the President of the United States is reiterating Russian propaganda?” Todd asked.

Alexander said yes.

“I think that’s a mistake,” the senator continued. “I think we need to be sensitive to the fact that the Russians are out to do no good, to destabilize Western democracies, including us, and be very wary of theories that Russians come up with and peddle.”

Alexander, widely seen as one of a few swing votes, helped cinch the GOP effort to block a Democratic motion to call witnesses during the impeachment trial. He announced Thursday, after the final day of the trial’s question-and-answer portion, that he would vote against the motion because he doesn’t need any more evidence to know what Trump did.

The Senate ultimately voted 51-49 to block witnesses. Just two Republicans ― Sens. Mitt Romney of Utah and Susan Collins of Maine ― joined Democrats in voting in favor of the motion.

Republicans have been twisting themselves into knots to justify acquitting Trump. Sen. Joni Ernst (R-Iowa), during an appearance Sunday on CNN’s “State of the Union,” danced around questions about whether Trump was “wrong” to ask Ukraine to investigate Biden.

“I think ferreting out corruption is absolutely the right thing to do,” Ernst said. “It’s probably something that I wouldn’t have done.”

Host Jake Tapper noted that Trump never mentioned the word “corruption” during his July 25 call with Zelensky.

“If it’s not something you would have done, why wouldn’t you have done it? Because it was wrong? Because it was inappropriate?” Tapper pressed.

“I think, generally speaking, going after corruption would be the right thing to do,” Ernst said. “He did it maybe in the wrong manner. But I think he could have done it through different channels.”

"I think generally speaking, going after corruption would be the right thing to do, he did it maybe in the wrong manner. But I think that he could have done it through different channels," Republican Sen. Joni Ernst says about President Trump. #CNNSOTU pic.twitter.com/sf2a77T3Gu — State of the Union (@CNNSotu) February 2, 2020