CNN’s expert data analyst Harry Enten has warned Democrats that their lead in national polls is soft, and doesn’t guarantee them a House majority. Looking back at polling data from before the 2006 and 2018 midterms, Enten identified a statistic that he believes should worry Democrats. Averaging recent CNBC and Washington Post polling, Enten found that the Democrats are four points up in generic national polls, but that’s not a big enough lead to guarantee success, falling well below where they were polling ahead of House takeovers in 2006 and 2018. In 2006, the Dems led by 12 points at...