Polls are open in a special election for a vacant state Senate seat in politically divided suburban Pittsburgh where the sides are testing some national themes ahead of 2020’s presidential election. Tuesday’s contest pits Republican D. Raja against Democrat Pam Iovino for a seat largely controlled by Republicans the past half-century, but the district is viewed as increasingly friendly to Democrats. On Monday, Republicans issued a robocall by Donald Trump Jr., urging listeners to vote for Raja.