Congressional Republicans slammed President Joe Biden's "angry" State of the Union address on Thursday night, claiming it furthered concerns over both his age, at 81 years old, and his mental acuity. 

Biden spoke to a joint session of Congress for the final SOTU address of his term, emphasizing the threat he said his predecessor, former President Donald Trump, poses to democracy. 

But for many Republican lawmakers, their takeaway was Biden's heavily-scrutinized mental faculties. 

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President Joe Biden delivered the State of the Union address to a joint session of Congress at the Capitol, Thursday, March 7, 2024

President Joe Biden delivered the State of the Union address to a joint session of Congress at the Capitol, Thursday, March 7, 2024 ((Shawn Thew/Pool via AP))

"A lot of the time it was hard to understand what he was saying," said House Freedom Caucus Chairman Bob Good, R-Va. "He was kind of mumbling and slurring." 

"We couldn't understand him. He was so mad," agreed Sen. Roger Marshall, R-Kan. "The volume was up and down."

At several points, Biden did raise his voice to emphasize his points, particularly when referring to Trump. 

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Biden State of the Union address

Some Republicans criticized Biden's delivery as too angry (Shawn Thew-Pool/Getty Images)

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Marshall added he was "very concerned" about Biden's health. 

Rep. Stephanie Bice, R-Okla. observed: "He kind of slurred over words occasionally."

"It was a long speech. He had a teleprompter. I think that helps," she said. 

Sen. Ted Cruz, R-Texas, remarked the president's annual address was "reminiscent of an old, angry man standing on his porch screaming ‘get off my front lawn.’"

President Joe Biden arrives for the State of the Union address on Capitol Hill, Thursday, March 7, 2024, in Washington, as Vice President Kamala Harris and House Speaker Mike Johnson of La., watch. 

President Joe Biden arrives for the State of the Union address on Capitol Hill, Thursday, March 7, 2024, in Washington, as Vice President Kamala Harris and House Speaker Mike Johnson of La., watch.  (AP Photo/Mark Schiefelbein)

According to Rep. Tim Burchett, R-Tenn., Biden assured the country Thursday night "that he does in fact have mental problems."

"He was yelling the whole time," reiterated Sen. Bill Cassidy, R-La.

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While Republicans tended to regard Biden's address as angry and evidence of his cognitive decline, congressional Democrats believed his speech showcased his energy. 

President Joe Biden delivers his State of the Union address to a joint session of Congress, at the Capitol in Washington, Thursday, March 7, 2024.

President Joe Biden delivers his State of the Union address to a joint session of Congress, at the Capitol in Washington, Thursday, March 7, 2024. (AP Photo/J. Scott Applewhite)

The president was "Very energetic. Very engaged. Very forceful and very optimistic," said Sen. Chris Coons, D-Del.

Sen. Elizabeth Warren, D-Mass., also praised Biden's delivery, remarking, "He was feisty!"

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"He was great. He was really fantastic," said Sen. Brian Schatz, D-Hawaii, who also described Biden as "energetic" and "clear." 

Even Republican Rep. Ryan Zinke, R-Neb., conceded: "I think in fairness, [Biden] had a good night."