Democrats controlled the U.S. House for 40 years until the Republican Revolution of 1994, after which it has changed hands repeatedly. After regaining control in the 2010 midterm election, Republicans have held the House by comfortable margins.

The GOP has a 59-seat majority over the Democrats. Even if Democrats achieve major victories down the ballot this November, most forecasters say it is unlikely Democrats will pick up the 30 seats necessary to win control of the House.

Three vacancies have opened up this year, representing two Democratic seats and one Republican seat.

Minnesota accounts for just eight of the nation's House districts, but several are competitive this year, including races in CD2, CD3 and CD8.

The Cook Partisan Voter Index (CPVI or PVI) measures how Democratic or Republican each state or district leans by comparing a party's voting percentage with the national average from the past two presidential elections. The PVI assigns rank according to these scores to describe how a district leans politically. We included the PVI score for each of Minnesota's congressional districts in the profiles below.

A lawmaker may be vulnerable if he or she does not fit his district’s partisan profile. Rep. Collin Peterson, for instance, is a DFLer in a district that has a PVI score of R+6.The least competitive districts have high PVI scores for an incumbent candidate's party. For instance, Rep. Keith Ellison in CD5 and Rep. Tom Emmer in CD6 represent relatively safe districts with high PVI scores for Democrats and Republicans, respectively.

Sources: Minnesota Secretary of State, U.S. Census Bureau, Federal Elections Commission, Cook Political Report, Center for Responsive Politics