WASHINGTON — Democrat Doug Jones of Alabama was sworn into office Wednesday, shrinking the Senate’s Republican majority and leading lawmakers of both parties to plead for more bipartisanship as Congress tackles pressing issues in advance of the 2018 midterm elections.

Vice President Mike Pence administered the Senate’s oath of office to Jones, the first Alabama Democrat elected to the Senate in a quarter century, and to former Minnesota Lt. Gov. Tina Smith, who was appointed to replace Sen. Al Franken, who resigned amid allegations of sexual misconduct.

Two former vice presidents, both Democrats, were there to support the Senate’s newest members as the GOP majority narrowed to 51-49. In future party-line votes, Republicans cannot afford more than one defection.

Jones was escorted to the Senate chamber by former Vice President Joseph Biden, who had headlined Jones’ campaign kickoff rally. Jones defeated Republican Roy Moore in a special election rocked by allegations of sexual misconduct against Moore.

Former Vice President Walter Mondale, along with Sen. Amy Klobuchar, D-Minn., escorted Smith to the Senate floor. She becomes the 22nd woman currently serving in the Senate, a record.