Darrell Issa is the latest in a series of House Republicans to depart Congress after this term, he announced Wednesday. His seat in southern California is particularly vulnerable for the party in 2018, as Hillary Clinton won his district by 7.5 points.
Outlier check: There are now 28 retiring representatives. The average number over the last five election cycles has been 23. Over that time, there has been more attrition from Republicans than from Democrats, however, the 3-to-1 ratio of retiring Republicans to Democrats this cycle is considerable.