The big unknown behind Democrats' polling leads
Poll after poll spells trouble for GOP candidates — in purple states and deep-red ones alike — but while Democrats see a blue wave coming, some Republicans see a polling mirage. Why it matters: Pollsters worry they're flying partly blind. Even a modest polling error could mean the difference between Republicans retaining control of Congress and President Trump facing Democratic majorities in both chambers. The big picture: Polling Trump voters has long been notoriously difficult. The polls unde…


