Democratic presidential candidate Bernie Sanders speaks at a recent event at the University of Chicago. (Scott Olson/Getty Images)

Sen. Bernie Sanders (Vt.) underwent an elective outpatient hernia repair procedure on Monday at George Washington University Hospital, his spokesman said.

The Democratic presidential hopeful was "doing fine" and is expected to resume his Senate duties on Tuesday and return to the campaign trail later this week, according to spokesman Michael Briggs, who said the surgery had been scheduled "for a while."

Briggs said Sanders returned to his house on Capitol Hill by early evening Monday. His first words after coming out of the recovery room were "Medicare for all," a reference to his universal health-care plan, Briggs said.

Sanders, 74, was campaigning as recently as Sunday night, participating in a Democratic event in New Hampshire with Hillary Clinton and former Maryland governor Martin O'Malley. Sanders has said in recent interviews that he is blessed with good health.