So Sen. Mitch McConnell (R-Ky.) has survived his primary challenge and will move on to the general election in November. How likely is he to win that? If the recent history of incumbent reelection is any guide: pretty likely.
There's been a lot of talk about the power of incumbency today, not surprising given the dominance with which McConnell was re-nominated by his party and the success of Rep. Mike Simpson (R-Id.), who at one point seemed like he might struggle against a tea party-backed challenger. (He did not.) Politico suggested that, despite the climbing cost of defending a seat, Tuesday night's primaries "reassert[ed] a once-iron law of politics: It’s awfully hard to oust a sitting member of Congress who’s willing to fight for his seat."
If that law was not set in iron, no one told past incumbents. While winning Senate races has gotten more expensive over time, incumbents have been reelected 88 percent of the time on average since 1990. Incumbents are likely to win by a wider margin, too. Since 2004, incumbents have won by an average of 29 percent. Overall, Senate winners have won by about 19 percent.
Here are the three graphs (cobbled together using Open Secrets data) that will help McConnell (and every other Senate incumbent) sleep well tonight. How they sleep once polls show up in late October, however, is another question.
Click the tabs to switch between graphs.