Yes. I did a study a few years ago in the U.K. I got access to three general elections' worth of party census data on everybody who sought to be a candidate for the British Labour Party. I also got some data from the Conservative Party and from the Lib Dems as well. This included everybody who came forward, both people who were selected and people who were not.
I did some surveys. I put together about 44 variables that we associate with the ideal candidate type and tested those. I tested things like ethnicity, race, sexual orientation, income, profession, education, and how much money was spent on nomination processes—all those kinds of things.
Only three variables of the 44 mattered in terms of who was selected and who was not. The first was sex: party members were much more likely to select men over women. Again, all of the variables were held constant and were controlled for. The second was being local to that constituency. The third was having a seat previously on local council, which is another kind of local measure.
Of the 44 variables that we think matter, only three really do, with sex being the most important, and in all seat types.