A dozen states hold primaries today, picking candidates for Congress and governor for the fall in a campaign season marked by economic woe and political upheaval.

Two senators and two House members have been denied renomination in earlier races — one from each party in each house of Congress. Among Republicans, tea party activists have changed the course of several other races to the consternation of the party’s establishment.

In a year of danger for incumbents, U.S. Sen. Blanche Lincoln, D.-Ark., is the most prominent of those in trouble in the week’s races.

Republican Gov. Jim Gibbons in Nevada faces a difficult challenge for renomination after a term marked by a messy public divorce. Among Democrats, California Rep. Jane Harman has a liberal challenger in her heavily Democratic district.