“As Republican members of Congress, we took pride in representing a political party that stood for honest and principled public leadership in which the American people could place their trust,” it read. “Sadly, our party's nominee this year is a man who makes a mockery of the principles and values we have cherished and which we sought to represent in Congress.”
This is obviously an unusual development. But it's worth noting that the 30 signatories are not exactly the best representatives of the Republican Party of 2016.
Seventeen of them come from blue states, mostly states that President Obama won by 10 to 20 points in 2012. Only two served since the tea party wave election of 2010. For the most part, the politics of the 30 were less conservative than their colleagues in the House even at the time, much less today. We can visualize this using VoteView's DW-NOMINATE scores.
Each string of points is the voting record of one of the members of Congress who signed the letter.
Of the 100-plus years these 30 members of Congress served cumulatively in the House and Senate, in only four of those years were the members of Congress more conservative than the average member of the House in 2013-2014.
One of those more-conservative members of the House was former congressman Bob Inglis of South Carolina. Inglis lost in that tea party wave, despite being reliably conservative. (The winner? Rep. Trey Gowdy.) Inglis blames his loss on having spoken out about the need to address climate change.
Another of the more-conservative members of Congress was former senator Gordon Humphrey of New Hampshire. Humphrey has been outspoken in his opposition to Trump, calling him a sociopath and saying that he might instead vote for Hillary Clinton.
For the most part, though, the Republicans who signed the letter are far less conservative than the average member of the current House, and were less conservative than the average of the Republican caucus while they were serving. They are largely part of the more centrist Republican Party that a healthy chunk of the base of the party has been railing against for the past few years.
In other words, if the goal was to lure Trump supporters away, this letter won't do the trick. If, on the other hand, the goal is to remind more-moderate Republicans that they have good reason to be skeptical of Trump's candidacy — a pitch that Clinton has been making for some time — this is the crew for the job.