Sen. Ben Nighthorse Campbell (R-Colo.) checked himself into George Washington University Hospital this morning after experiencing mild chest pains.

“Initial diagnosis indicates the source of pain is non-cardiac,” the 70-year-old Senator’s office said in a statement. “Senator Campbell is resting comfortably. Upon completion of a thorough evaluation, he is expected to resume normal Senate activities later this week.”

The word of Campbell’s health comes after a week of potentially damaging stories about the resignation last Friday of his long-time chief of staff, Ginnie Kontnik, who was accused by a former subordinate of demanding kickbacks. The matter has been referred to the Senate Ethics Committee, and Democrats and government watchdog groups are demanding a federal probe.

Campbell last fall revealed that he was being treated for prostate cancer.

His bid for a third term, once considered a foregone conclusion, may get tougher on Sunday, when Rutt Bridges, a wealthy philanthropist, is expected to announce that he is entering the Democratic Senate race.