With the advent of this election year, the time to turn from generalities/playing field pieces to tracking specific races is fast approaching. But before picking up my series on competitive Senate races (I wrote on three with relatively well-formed dynamics last year: Kentucky, Montana, and Arkansas), I do have a few more things to say about the playing field. As a general matter, the journalistic narrative hasn’t yet caught up with the deterioration of the Democrats’ political standing since the early summer. Polls showing tight Senate races in New Hampshire, Iowa, Colorado and Michigan are met with surprise and disbelief....