Contested Republican primaries are nothing new. In 2022, 33 incumbent Republicans drew primary challengers. Aside from the relatively quiet 2020 primary, an average of 25 incumbent Republican legislators have faced contested primaries. With less than two weeks left until the filing deadline, at least 38 Republican incumbents have drawn at least one primary challenger.Historically, primary challenges have not been motivated by singular events or votes. Battles between self-identified “true conservatives” and incumbents they called “RINOs” have characterized some of the more prominent primary challenges over the past decade and a half. However, this vague conflict was never a common denominator unifying the intraparty opposition.This year feels different. The central conflict isn’t being defined by vague pronouncements over who is more conservative. Instead, it is largely being defined by a single vote: the impeachment of Atty. Gen. Ken Paxton. Nearly as many House Republicans (60) voted to impeach Paxton as Democrats (61). Four of the Republican aye votes are not seeking re-election as of this writing. Of the 56 who are seeking re-election, 33 (59%) have at least one announced or filed primary challenger. Of those, 10 have at least two primary challengers. I expect most of the other 23 will also draw at least one challenger before the filing period ends in two weeks.As for the 21 Republicans seeking re-election who did not vote to impeach Paxton, only five (24%) have drawn primary challengers so far.Not only are many challengers citing the Paxton vote as a reason to support their candidacy, but Paxton himself is getting involved in these races. He has endorsed at least 11 of the primary challengers of House Republicans who voted to impeach him. He has also endorsed several of the House Republicans who voted against impeachment.It remains to be seen whether the challengers can marshal this early pro-Paxton momentum into strong campaign finance results, but it seems likely that past large donors to challengers endorsed by scorecard conservative groups would place bets on candidates endorsed by Paxton at the very least.It also remains to be seen whether these challengers will be able to oust significantly more incumbents than in a typical primary election. Only twice since 1996 – 2012 and 2014 – have more than four Republican incumbents fallen in primary elections. None have fallen in the primary since 2018 (Runoffs are another matter.).It further remains to be seen whether the Paxton impeachment issue plays any significant role in open-seat primaries. This seems less likely, but it something to watch as primary races heat up.