The Senate elections were part of the Democratic sweep of the 2006 elections, in which Democrats made numerous gains and no congressional or gubernatorial seat held by a Democrat was won by a Republican. However, Democratic incumbent Joe Lieberman in Connecticut was defeated in the primary but was reelected as a third party candidate; he continued to caucus with the Democrats. Because of this, this is the first time since the 1970 Senate elections in which a member of a third party, who is not an independent, was elected to the Senate. Independent Jim Jeffords in Vermont retired, but was succeeded by another Independent, Bernie Sanders, retaining their presence in the Senate. Jeffords and Sanders both caucused with Democrats. This election was also the first midterm election since the 1990 midterms and the most recent one to date in which Senate Democrats made net gains and the first midterm election in which they made more than one net gain since 1988. Democrats picked up six seats, all via the defeats of incumbents, in Missouri, Montana, Pennsylvania, Ohio, Rhode Island and Virginia, while holding open seats in Maryland and Minnesota. Republicans held their sole open seat in Tennessee.