State legislative special elections provide an interesting index of partisan sentiment these days. That wasn’t so in the late 20th century, when clever local candidates and notables often got voters to cross party lines. But in this century of increasing partisan polarization and straight-ticket voting, local special elections are a proxy for opinion on national issues. In that light, consider the results of the two special legislative elections that have resulted in a change of parties so far this year.  The first was in Connecticut’s 36th state Senate district on Aug. 17. This is the richest state Senate district in…