Some of this is due to the DC press being wired for Republicans (why that is too much for the margin of this blog post), but Democrats do need to think about why even when the have the presidency and the Senate (and even when they had the presidency and the Senate AND the House), politics is always presented The Republican Show.
Sure some of this is the fault of the press, as I said, but you go to politics with the press you have and not the press you want. It isn't that I think it's a problem that can be fully solved, but it's certainly something they can improve on.
Always better to be on offense than defense, and while you can't possibly distract the press from the shiny toy of a presidential primary, you can use the opportunity to point how how all those Republicans really suck.
