In today’s LA Times:
[A]ll [California] primary elections, including for members of Congress, will take place in March. California is now an outlier — all but eight states hold congressional primaries much closer to the general election, often in June or August….
Early primaries have the effect of insulating incumbents. If incumbents see no serious competitors after an early filing date, they may decide to act without regard to constituents — for example, when called upon to vote for or against impeachment.