Rep. John Yarmuth John Allen YarmuthPelosi, Democrats unveil bills to rein in alleged White House abuses of power GOP, White House struggle to unite behind COVID-19 relief House seeks ways to honor John Lewis MORE (D-Ky.) slammed Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellDemocratic senator to party: 'A little message discipline wouldn't kill us' House to vote on resolution affirming peaceful transition of power Republican lawyers brush off Trump's election comments MORE (R-Ky.) this week over his approach to politics, arguing the Kentucky Republican was focused primarily on expanding his power.

When asked what drives McConnell politically, Yarmuth responded, “power — pure and simple.”

“It’s unfortunate because it’s power without a purpose. It’s power for power’s sake,” Yarmuth, who has known McConnell since 1968, told Hill.TV on Monday.

“He doesn’t really have any core principles,” Yarmuth added. “You can find almost no legislation in his 35 years with his name on it.”

When reached for comment Tuesday, a spokeswoman for McConnell pointed to previous remarks by the majority leader.

"As the only one of the four congressional leaders who isn’t from the coastal states of New York or California, I view it as my job to look out for middle America and of course Kentucky in particular," McConnell said. "That means I use my position as Majority Leader to advance Kentucky’s priorities.”

Yarmuth also acknowledged McConnell's success, jokingly referring to him on Monday as the “Tiger Woods of politics.”

“He’s the most focused politician I’ve ever seen,” Yarmuth said. “That makes him very formidable, and he’s smart. He’s very smart politically and he understands how the games are played.”

McConnell, who became Senate majority leader in 2015, has been fiercely protective of the GOP majority in the upper chamber, where Republicans hold a 53-47 advantage.

Earlier this year, he vowed to be the “Grim Reaper” of progressive legislation being passed by the House.

"If I'm still the majority leader in the Senate, think of me as the Grim Reaper. None of that stuff is going to pass," he said in April.

McConnell is up for reelection next year, when he's like to face Amy McGrath, the Democrat who nearly flipped a conservative House district in Kentucky in 2018.

Though McConnell is unpopular in his home state, according to Morning Consult polling, McGrath will face an uphill battle against the longtime senator in the deep-red state.

—Tess Bonn

Updated at 4:05 p.m.