President Biden’s agenda has hit a snag in the U.S. Senate, as medical-related absences for two Democrats have left his party without the critical 51-vote threshold it secured in last year’s midterm elections.

Sen. Dianne Feinstein, D-Calif., has been hospitalized with shingles and likely will not return until "later this month," the 89-year-old said in a statement Wednesday.

Meanwhile, Sen. John Fetterman, D-Pa., is receiving treatment for clinical depression, and it is not yet clear when he will return. Those absences leave the fate of Biden’s legislative priorities and judicial nominees up in the air — at least temporarily.

"The danger of having such a small majority is that one or two illnesses can bring things to a halt. The administration has been aggressive and effective on judicial nominees, but that’s all on hold for now,’ political strategist Doug Heye told Fox News Digital.

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Feinstein, Fetterman and Biden

The medical-related absences of Democrats Dianne Feinstein, left, and John Fetterman, center, could leave President Biden's agenda at a near standstill in the Senate. (Getty Images)

In addition to Feinstein and Fetterman, two more senators also missed votes while away from Capitol Hill this week.

Sen. Jeff Merkley, D-Ore., said Monday that he would be in Oregon for a "family matter" but would return "as soon as possible." His mother died Tuesday. On the other side of the aisle, Sen. Mike Crapo, R-Idaho, has been out due to a reported illness.

The president and his allies have celebrated the fast-paced court confirmations they have enjoyed over Biden’s first two years in office. Democrats were buoyant earlier this month after confirming 100 judicial nominees to lifetime appointments. In his first year alone, Biden got more lower-court picks confirmed by the Senate than any past president since President John F. Kennedy, according to an analysis by the Brookings Institute.

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Jeff Merkley

Sen. Jeff Merkley, D-Ore., was back home in Oregon this week due to the death of his mother.

However, this week’s absences have left the Senate with an even 48-48 split, forcing Vice President Kamala Harris to head back to Capitol Hill to cast tie-breaking votes that got Biden’s nominees over the finish line. If Merkley and Crapo return shortly, the Senate will still be stuck in a 49-49 tie.

However, Biden's judicial nominations, in particular, could take a longer-term hit. Feinstein is a member of the Senate Judiciary Committee, which vets all the president’s court picks, and that committee canceled a planned business meeting set for Thursday morning.

DEMOCRAT SEN. FETTERMAN’S OFFICE RELEASES UPDATE AFTER HE CHECKS HIMSELF INTO HOSPITAL FOR CLINICAL DEPRESSION

Vice President Kamala Harris speaks in Arizona

Vice President Kamala Harris was forced to act as a tie-breaker for President Biden's judicial nominees last week, as the Senate was split 48-48 due to multiple absences. (AP Photo/Alberto Mariani)

Hours later, Feinstein said in a statement, "I was diagnosed over the February recess with a case of shingles. I have been hospitalized and am receiving treatment in San Francisco and expect to make a full recovery. I hope to return to the Senate later this month."

As of Friday morning, the committee has not listed any upcoming hearings or meetings regarding judicial nominations.

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The most recent update from Fetterman’s spokesman, Joe Calvello, was released on Monday, though he admitted there was not much new information to offer.

"We understand the intense interest in John’s status and especially appreciate the flood of well-wishes. However, as we have said this will be a weeks-long process and while we will be sure to keep folks updated as it progresses, this is all there is to give by way of an update," Calvello said.