(CNN) Senate Majority Leader Mitch McConnell defended himself from withering criticism by Democrats and political commentators that his blockade of election security legislation is un-American, calling it "modern-day McCarthyism."

In a spirited speech on the Senate floor Monday, the Kentucky Republican turned his sights on opinion columnist Dana Milbank and MSNBC host Joe Scarborough, who respectively called McConnell on Friday a "Russian asset" and "Moscow Mitch."

McConnell said that he has been tough on Russia for more than three decades, from supporting President Ronald Reagan's strategy on missile defense to greenlighting the bipartisan Senate investigation into Russian interference in the 2016 elections. He said Democrats and Republicans had spontaneously applauded at a closed-door meeting he helped set up a few weeks ago when officials discussed all the "progress" that had been made since then. And he noted that he supported the hundreds of millions of dollars Congress has sent to the states to boost their election infrastructure.

"American pundits calling an American official treasonous because of a policy disagreement," McConnell said. "If anything is an asset to the Russians, it is disgusting behavior like that."

For months , the left has criticized McConnell for countering in 2016 a proposal by the Obama administration to warn state election officials about Russian interference in the election; he reportedly agreed to send a vaguer letter regarding "malefactors" who sought to "disrupt" the election.

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