2018 Massachusetts Senate - Diehl vs. Warren

For years, Massachusetts was one of the most solidly Republican states in the nation. From the founding of the Republican Party through 1928, the state voted for only a single Democrat, in 1912, when the Progressive wing of the Republican Party split off to form a short-lived third party.  But as time passed and more and more Irish and other minorities moved to Boston, the Democrats' strength grew.  By the late 1800s Boston was a mostly Democratic city, by the 1930s the state was Democratic in national elections, and by the 1960s it was donkeys all the way down.

Today the Republican Party is now virtually extinct in the state legislature, and the state hasn't sent a Republican to the House of Representatives since 1996.  But in January 2010 the political world was shocked when an obscure state senator defeated Attorney General Martha Coakley in a special election to claim Ted Kennedy's seat by a five-point margin.  Coakley won the solidly liberal western portion of the state and Boston, but it wasn't enough to offset Scott Brown's margins in the suburbs. 

Brown was defeated by law professor Elizabeth Warren, who has emerged as one of the most solidly liberal members of the Senate. Warren remains popular in the Bay State, and Republicans have failed to find a challenger who poses a threat.