With the 2014 primary season concluding Tuesday, we pulled data on the five most recent primary seasons to see how much that incumbent effect changed over time. The good news: Races are getting closer! The bad news: Only under a very particular subset of conditions. And they're not getting very much closer. But, still!
The average margin of victory for winners of House primaries in 2014 topped 77 percent; for the Senate, it was nearly 70.
But that's in large part because a lot of people win uncontested primaries, giving them 100 percent of the vote. And the number of uncontested House races has dipped a bit recently, but is still high.
The number of uncontested Senate races is lower, in part because they're statewide. And, in part, because there are more minor-party primaries on the House side. (Yes, we included third-party primaries; this is America, after all.)
When you look only at contested races, the margin on both sides dropped substantially. But, interestingly, the margins of victory on the House side remain fairly consistent over time, while Senate races fluctuate.
Since Senate races apply to entire states, it's not surprising that the raw vote difference between Senate candidates (in contested races) varies more -- and is much larger -- than in House races.
If you're curious about the value of your vote, there have been three races since 2006 that have been settled with 10 votes or fewer. Just over 30 have been settled by 100 votes; almost 200 by 1,000 votes or fewer. Which, again, includes minor party campaigns.
So, to recap: Get elected to office from a major party to the Senate, and you're likely to win your reelection by 50 percentage points -- if anyone bothers to run against you. Please send checks for that great campaign advice to: Philip Bump, c/o Washington Post, Washington, D.C. Thanks in advance.