Former Democratic Sen. Claire McCaskill criticized Sen. Ron Johnson, R-Wis., claiming that he was misspending his time on former Vice President Joe Biden's son when he should be focusing on the coronavirus.

"Allow me to pop off on Ron Johnson here," McCaskill said on Wednesday's "Morning Joe."

"What a joke! What an embarrassing tool! He is chairman – think about this – chairman of the Homeland Security Committee! Right? He has jurisdiction over coronavirus and the federal response," she added.

McCaskill's comments came after Johnson indicated that he would force a vote on subpoenaing Hunter Biden in relation to the senator's investigation into Burisma Holdings, the Ukrainian gas company at the center of corruption suspicions surrounding the Bidens.

"Is he calling a hearing? Is he trying to figure out why first responders’ tests aged on a shelf in the state of Washington until they were no longer good?" McCaskill asked.

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"Is he going to tell people why they can’t get the test? No. Even though it's not in his committee’s jurisdiction — the Judiciary Committee is not issuing subpoenas on Hunter Biden. The Foreign Affairs Committee is not issuing subpoenas on Hunter Biden. No! This joke, Ron Johnson, is actually politicizing a committee that right now should have one focus: what is going on with the United States of America federal response to the coronavirus? People should be really angry about this."

McCaskill eventually provoked laughter from the "Morning Joe" panel when she asked: "Can you tell it makes me mad? I am so mad about it."

On Twitter, McCaskill railed against the president's response to the coronavirus, arguing that he was making conditions more dangerous for older Americans.

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"In his insistence on 'keeping the numbers down,' Trump is actually making it worse and risking older Americans’ health," she tweeted.

McCaskill appeared to claim victory Wednesday afternoon, crediting herself with Johnson’s decision to delay a vote on the Hunter Biden subpoena.