In a special preview for Axios readers, here's a new analysis by David Wasserman of Cook Political Report, unpacking the GOP's daunting math: "With 102 days to go, Democrats remain substantial favorites for House control. A big reason: Republicans are defending 42 open or vacant seats, a record since at least 1930." (After the March victory by Democrat Conor Lamb in Pennsylvania, Democrats need to flip 23 seats to take the House). "Of Republicans' 42 incumbent-less seats, eight are in districts that voted for Hillary Clinton in 2016, and an additional 13 are in districts where President Trump received less...