The Republican race for president remains as wide open as ever. You can see that by looking at endorsements, which are highly correlated with the final result of a primary. Very few Republican bigwigs have endorsed a candidate.1 Among those members of Congress who have endorsed a candidate, however, a pattern is emerging: The endorser’s ideology is very similar to that of the candidate he or she is backing. Moderate members of Congress are endorsing moderate candidates, and very conservative members are backing very conservative candidates (not counting home-state endorsements).
That’s good news for Marco Rubio, if it holds through the rest of the primary season.
You can see why in the chart below, which shows the average ideological score of each candidate’s endorsers, according to DW-Nominate, an algorithm that uses roll call votes to rate members of Congress on a liberal-conservative scale (on the chart, 100 is the most conservative and -100 is most liberal). The chart also shows each candidate’s ideological rating according to our three-ingredient cocktail, which combines DW-Nominate scores, Adam Bonica’s fundraising-based scores and OnTheIssues.org’s public statement grades. Keep in mind that most Republican members of Congress haven’t endorsed yet.
The correlation between a candidate’s ideology score and the average one of his or her endorsers is strong, 0.952 (again, I’m not counting home-state endorsements). And among the major contenders, Rubio’s ideology is closest to the center of the Republican Party; about 40 percent of Rubio’s backers are to the right of the average congressional Republican, while 60 percent are to the left. So if the ideological matching continues, Rubio will have the biggest pool to draw from.
Compare Rubio to the other four candidates currently leading the polls: Jeb Bush, Ben Carson, Ted Cruz and Donald Trump. Carson and Trump don’t have any endorsements. Bush and Cruz do, but they are drawn from a more narrow ideological faction.
Cruz is getting his support from the far right members of Congress. And even though the Republican Party has become more conservative, it hasn’t yet moved as far right as Cruz and his endorsers. Indeed, 85 percent of congressional Republicans are more moderate than Cruz’s current endorsers. The good news for Cruz: He’s unlikely to be outflanked on the right in the endorsement primary.
Bush has the opposite problem, as I’ve written previously: His average endorser is more liberal than 72 percent of all Republican members of Congress. Now, Bush has done a good job of locking up a lot of these more moderate members. But most of those endorsements came early in the campaign, and the endorsements Bush does have haven’t done him much good.
So will we continue to see Republican officials only endorse candidates close to them ideologically? It could be the case that members have so many choices — with Bobby Jindal’s exit this week, the GOP field is down to 14 candidates — that they don’t feel the need to compromise on a candidate in the middle of the party. That would be bad news for Rubio. But it’s also possible that, as the campaign progresses and more candidates drop out, endorsers will eventually bite the bullet and rally around one of the candidates. And Rubio, sitting in the center of the party, is in the best position to benefit.