Sen. Patrick Leahy, D-Vt., was taken to a hospital in Washington, D.C., for tests and will be hospitalized overnight "as a precaution," his office said Thursday evening. 

The 82-year-old senator was not feeling well at his residence in McLean, Virginia, late on Thursday. 

Sen. Patrick Leahy

Sen. Patrick Leahy, D-Vt., listens as Chairman of the Joint Chiefs of Staff Gen. Mark Milley and Secretary of Defense Lloyd Austin testify before the Senate Appropriations Committee Subcommittee on Defense, May 3, 2022, on Capitol Hill in Washington. (Amanda Andrade-Rhoades/The Washington Post via AP, Pool, File)

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He'll remain hospitalized for observation overnight. 

Leahy, the longest-serving member of the U.S. Senate, announced last year that he will retire at the end of his term. 

This is a breaking news story. Check back for updates.