Jay Cost (H/T: @MelissaTweets) has written an article on the Democratic party that is impossible to excerpt properly:
So, you've decided to become the leader of a big political party. Only one problem: it's too big! What to do?
Well, you've come to the right place. Here at the Horse Race Blog, we've developed a three-step guide to making that broad party a little more...narrow. Just follow these simple instructions and your majority party will be smaller and a little easier to handle in no time!
...and summarizing said article (the very short version: it's a bad idea to run a national party as if it were an urban regional one) doesn't do it justice. Instead, I suggest that you first read it, then take a look at the maps after the fold.
First is a color-shaded map of the legislators who voted for the Stupak amendment to the healthcare rationing bill. Data via this site - and note that the sentiments found there are fairly representative of the Online Left on both the Democratic members of Congress who voted for Stupak, and the ones that voted against health care rationing:
Second is a color shaded map of all the Members of Congress who voted against health care rationing. Data via here - and note that the Times helpfully points out that virtually every no Democratic vote is considered vulnerable in 2010 (usually by being in a district that John McCain won, which generally means a non-urban one):
Note the broad swath of purple across the South, and the smaller one in the Rustbelt and Southwest. Note the eager willingness of Democratic activists to target already vulnerable Democrats in both Republican and battleground states - or, for that matter, Democratic ones. Note that even in Democratic states there is evidence of a split in opinion between urban Democrats and suburban/rural ones.
And finally, note that Jay Cost may indeed know what he's talking about.