Interesting analysis with data from Nataniel Rakich @baseballot on the limited risk incumbents face in primary elections, even when party voters are generally unhappy with their party.

The Democratic Party’s current +55-point net favorability rating among its own members is similar to the Republican Party’s net favorability rating among Republicans in 2009. In an average of four CNN polls that year, the GOP had a net favorability rating of +54 points among its own members. That, of course, coincided with the rise of the Tea Party and four Republican members of Congress (two senators and two representatives) losing renomination the following year.

On the Democratic side, intraparty satisfaction has been this low at this point in the cycle only once in the past 16 years: in 2017, following a year of infighting between supporters of former Secretary of State Hillary Clinton and Sen. Bernie Sanders. In an average of four CNN polls conducted that year, Democrats gave the Democratic Party a net favorability rating of +58 points. The following election saw the rise of the “Squad,” as progressive Reps. Alexandria Ocasio-Cortez and Ayanna Pressley defeated entrenched Democratic incumbents….

The reality is, a few members of Congress lose their primaries every election cycle, but it’s rarely more than a handful. According to data collected by Bloomberg’s Greg Giroux, in the average cycle since 1990, six members of Congress have lost renomination.

And low intraparty net favorability ratings in the year before the election haven’t historically led to a lot of incumbents losing their primaries. For example, both the Democratic and Republican parties were relatively unpopular among their own members in 2017, but only five incumbents lost renomination in 2018. Then, both Democrats and Republicans became much happier with their parties in 2019 — but eight incumbents lost renomination in 2020.

The lack of a relationship here isn’t too surprising. When you look more closely, most incumbents who lose in primaries do so for specific reasons, like scandals, redistricting, or simply getting caught napping — not national trends. Indeed, incumbent primary losses always spike in years ending in 2, which, of course, are the first elections conducted after post-Census redistricting….

So we probably shouldn’t expect an unusual number of incumbents to go down in primaries next year. However, that doesn’t mean that the Democratic Party establishment can rest easy. The relatively high level of Democratic discontent could still manifest itself in open-seat races. The biggest impact of the Tea Party movement wasn’t incumbents losing primaries, but rather the proliferation of a new breed of uncompromising, anti-establishment conservatives that moved the Republican caucus right, obstructed legislation favored by GOP leadership, and ousted multiple speakers of the House. Similarly, MAGA-aligned legislators have displaced old-guard Republicans in Washington since President Donald Trump’s first election in 2016, predominantly not through defeating them in primaries, but succeeding them after they retired. Over on the Democratic side, most “Squad” members other than Ocasio-Cortez and Pressley — including Rashida Tlaib, Ilhan Omar, and Summer Lee — were first elected from open seats. And, of course, last week’s Democratic primary for mayor of New York City didn’t feature an incumbent either.