Over the weekend, a number of GOP lawmakers un-endorsed Donald Trump, with some going as far as calling on him to drop out of the race. What role did ideology play in the decision-making? Below is a chart that maps out the ideology (in the from of DW-NOMINATE scores) for the entire 114th House GOP caucus and whether the MC supports Trump (a value of 1 indicates support for the nominee while 0 means the lawmaker does not support the top-of-the-ticket). Data regarding support is found from this spreadsheet, compiled by @Taniel.
Moderates abandoned Trump in greater numbers than conservatives, though a few strong conservatives also walked away from the nominee. Another consideration comes into play — district competitiveness. Lawmakers hailing from competitive districts (who tend to be moderate) might risk electoral defeat at the hands of appalled independent voters if they continued to support Trump; those from solid-GOP districts, on the other hand, might risk alienating Trump voter and thus inviting a future primary challenge or, at worst, encouraging voters to skip down-ballot races, perhaps imperiling a reelection bid.
The below chart compares lawmaker ideology to the Cook Political Report’s district Partisan Voter Index — the evident trend of increased moderation as a district becomes more competitive (a PVI close to 0) is a well-documented phenomenon. Interestingly, a few lawmakers from safe districts have decided to un-endorse Trump. However, by and large, condemning and refusing to support Trump seems to be but a calculated political move dependent upon reelection, not party health or policy principles.