Democrats have seen their odds of a massive blue wave return over the past month to about where they were at the end of 2017, when President Trump was about as popular as drinking alone in Minnesota. But as with their polling nosedive earlier this year, which caused so much anguish on the left, it's not at all clear what is causing this uptick in the party's fortunes. No matter where you look, the numbers are better for Democrats than they were two months ago.