The 2014 vote is what’s known as a “six-year itch” election, with the party holding the White House usually losing a substantial number of House and Senate seats in the sixth year of its tenure. There are a variety of reasons, but at that midway point in a party’s second four years in the White House, the “in” party tends to lose energy and focus. Party leaders run out of ideas, and the “first team” in terms of personnel—the people who were there when the president took office—have often bailed out, and the second or third team is sometimes not as good. Voters tend to grow weary and to look for something different.

In the six “six-year itch” elections since World War II, the party in the White House has averaged a 29-seat loss in the House and a six-seat (actually 5.6) loss in the Senate. In 1958 (Eisenhower), 1966 (Kennedy/Johnson), and 1974 (Nixon/Ford), the party in the White House lost 48 seats; in 2006 (George W. Bush), the most recent such election, the party in power lost 30 seats. In 1986 (Reagan), the loss was just five seats, while in 1998, under Clinton, the “in” party actually gained five House seats—no doubt a backlash to Republican efforts to remove the president from office. In that same election, the Senate was a wash, and in the other five, losses ranged from four seats in 1966 and 1974 to six seats in 2006 and 12 seats in 1958…

[I]n the Senate, with only one Republican-held seat up (Susan Collins in Maine) in a state not carried by Mitt Romney by at least 8 points, the GOP seems to have little exposure. At the same time, Democrats have four seats in states that Romney carried by 15 or more points (Mary Landrieu in Louisiana, Mark Pryor in Arkansas, Jay Rockefeller in West Virginia, and Tim Johnson in South Dakota), with two more in states that Romney won by 14 points (Max Baucus in Montana and Mark Begich in Alaska) and two others in swing states (Kay Hagan in North Carolina and Mark Warner in Virginia).