No House incumbents lost their primaries on Tuesday. But that doesn’t mean their colleagues should rest easy.

In fact, the results of Tuesday’s primaries suggest that incumbents face an environment even tougher than they did in 2010, when four House members lost their primaries and three senators lost re-nomination.

If Tuesday is any indication, that number could rise significantly this year — particularly in the House.

Rep. Spencer Bachus ( R-Ala.) gestures during a news conference on Capitol Hill in Washington, in December 2009. (AP File Photo/Haraz N. Ghanbari)

Reps. Alan Nunnelee (R-Miss), Spencer Bachus (R-Ala.), and Jo Bonner (R-Ala.) all took between 56 and 59 percent of the vote in their primaries.

In the 2010 election, which was supposed by many to be an anti-incumbent year, just 20 House members were held below 60 percent of the vote in party primaries, including the four who lost.

After just three congressional primaries in 2010 (covering just 6 percent of the congressional map), we already have four incumbents who have fallen beneath that threshold.

We already knew more incumbents were going to lose this year, in large part because redistricting has given many of them new territory. That was a big reason Schmidt lost last week, and the new map also claimed Rep. Dennis Kucinich (D-Ohio), who lost to Rep. Marcy Kaptur (D-Ohio) in a combined district. (We’re not including Kucinich’s loss in the analysis above because he faced another incumbent — a special case.)

But the examples in Alabama and Mississippi are striking because all three incumbents experienced relatively minimal changes under their state’s new maps.

In other words, if we’re seeing this in Alabama and Mississippi, it’s game-on in states where incumbents are running in lots of new territory.

None of this is to say that dozens of House incumbents are going to lose this year. Even in the most anti-incumbent year, the vast, vast majority of incumbents will win re-nomination just because it’s so difficult to raise money and run a campaign against an incumbent in the primary.

But the combination of redistricting and the anti-incumbent fervor out there (combined with a new group spending money solely to defeat incumbents) is looking pretty potent, historically speaking.

And even if it isn’t enough to unseat lots of incumbents, it’s definitely enough to scare lots of them.

More from Post Politics:

A super PAC targets incumbents of any party

Santorum hopes ideology trumps electability

More ‘Medi-scare’ hooey from the GOP