The most significant vote in the U.S. House this year was on May 4, when the U.S. House passed a bill revising health care by four votes. No Democrat voted for the bill. Twenty Republicans voted against the bill. They include one from Arizona, one from Colorado, one from Florida, one from Kentucky, three from New Jersey, two from New York, one from North Carolina, two from Ohio, four from Pennsylvania, one from Texas, one from Virginia, and two from Washington. See this Roll Call story describing and listing each of these Republicans.

Classifying these twenty Republicans by the method in which they won the Republican nomination in 2016, one finds nine were nominated in a closed primary, five in a semi-closed primary, four in an open primary, and two in a top-two system.

This observation matches research conducted by political scientists, showing there is no correlation between type of primary system, and how elected officials behave. Here is an article by Jon Fleischman on why all fourteen Republican members of the House from California voted for the health care bill. Thanks to Rob Richie for suggesting this blog post.