John Fetterman

Pennsylvania Democratic Sen. John Fetterman's recent appearance at the Republican midterm convention has sparked speculation about whether he could leave the Democratic Party. Fetterman endorsed Republican Sen. Dave McCormick and praised bipartisan cooperation in a prerecorded video. He has said he will remain a Democrat.

But the episode raises a broader question: What happens when an elected member of Congress changes political parties?

Can an elected senator switch parties?

Yes. A senator or representative can change party affiliation without resigning from Congress. The U.S. Senate has a long history of lawmakers changing parties during their time in office.

A party switch does not automatically trigger a new election or remove the lawmaker from office. The member continues serving the remainder of their elected term.

Historical examples of party switching

The Senate Historical Office documents numerous examples of senators changing party affiliation during their Senate service.

South Carolina Sen. Strom Thurmond switched from Democrat to Republican in September 1964. He remained in the Senate until 2003.

In 2001, Vermont Sen. Jim Jeffords left the Republican Party and became an independent. He continued to caucus with Democrats, changing control of the evenly divided Senate from Republicans to Democrats.

Connecticut Sen. Joe Lieberman became an independent in 2006 after losing the Democratic primary. He won reelection as an independent and continued to caucus with Democrats.

Pennsylvania Sen. Arlen Specter switched from Republican to Democrat in April 2009. He continued serving in the Senate until 2011.

Does a party switch change who controls the Senate?

It can. The Senate's party balance is affected by how members affiliate and caucus.

Jeffords' 2001 switch is the clearest example: his decision to become an independent who caucused with Democrats gave Democrats control of the Senate.

A switch does not automatically transfer a seat to the other party. Fetterman would still be Pennsylvania's senator if he changed his affiliation. But his choice of party and caucus could affect the balance of power.

What happens to committee assignments and leadership?

Party affiliation can affect committee assignments, seniority and leadership positions. The Senate organizes its committees through party conferences, so a change in affiliation can have consequences beyond the label next to a lawmaker's name.

The details depend on the circumstances of the switch and the Senate's rules and agreements.

What would a Fetterman party switch mean?

Fetterman's appearance at the Republican convention and his rejection of socialism have fueled speculation about his political future. But he has said he will remain a Democrat.

The historical record shows that members of Congress can change parties while keeping their seats. Whether Fetterman will do so is a separate question.

For now, the fact check is straightforward: party switching is permitted, it has happened repeatedly in the Senate, and it can affect the balance of power without requiring a lawmaker to resign.