MT. LEBANON, Pa. — A razor’s edge separated Democrat Conor Lamb and Republican Rick Saccone Tuesday night in their closely watched special election in Pennsylvania, where a surprisingly strong bid by first-time candidate Lamb was testing Donald Trump’s sway in a GOP stronghold. The contest in the Pittsburgh-area district has drawn national attention as a bellwether for the midterm elections in November, when the Republican Party’s House and Senate majorities are at risk.