WASHINGTON — LAWYERS on average are much more liberal than the general population, a new study has found. But judges are more conservative than the average lawyer, to say nothing of the graduates of top law schools.

What accounts for the gap? The answer, the study says, is that judicial selection processes are affected by politics.

Judges are, of course, almost without exception lawyers. If judges reflected the pool from which they were selected based on politically neutral grounds like technical skill and temperament, the bench might be expected to tilt left.

But something else is going on.

“Politics plays a really significant role in shaping our judicial system,” said Maya Sen, a political scientist at Harvard’s Kennedy School of Government and one of the authors of the study. Since judges tend to be more conservative than lawyers, she said, it stands to reason that the officials who appoint judges and the voters who elect them are taking account of ideology. She said the phenomenon amounted to a politicization of the courts, driven largely by conservatives’ swimming against the political tide of the legal profession.