CLASH OF THE INTEREST GROUPS. The Hill doesn't draw this out in its reporting, but the juxtaposition of a couple of articles in today's edition shows the emergence of real power struggle within the Democratic Party between old and new interest groups in key races this fall. Alexander Bolton reports:

At least seven of the most vulnerable House GOP incumbents have been endorsed by unions, environmental activists or other Democratic-leaning advocacy groups. So have at least three of the most vulnerable Senate Republicans.

Organized labor has also poured tens of thousands of dollars into the campaign accounts of highly vulnerable Republicans, in several instances surpassing the amount given to Democratic challengers.

Rep. George Miller (Calif.), ranking Democrat on the Education and the Workforce Committee, has disclosed that at least one of his House colleagues has said that, if Democrats fail to capture the House, labor will be partly to blame....

Rep. Jim Gerlach (R-Pa.) is endorsed by the National Education Association and the Pennsylvania State Education Association, teachers unions that endorsed his Democratic opponent, Lois Murphy, in 2004. The Teamsters and the Delaware County chapter of the AFL-CIO have endorsed Rep. Curt Weldon (R-Pa.), a veteran lawmaker facing his toughest race in years....

In southern Connecticut, Rep. Christopher Shays (R), whom Democrats nearly defeated in 2004, collected $67,000 in labor contributions through April 25. Diane Farrell, the Democrat who nearly beat him two years ago, has garnered only $1,000 more in labor money.

Take a close look at those names and then check out Jonathan Kaplan's two pieces on Netroots-endorsed candidates and the potential impact of the Joe Lieberman-Ned Lamont race on down-ticket contests. From the Netroots story:

It�s unclear how their endorsements will affect the outcome in several competitive open-seat races, such as in Pennsylvania, where Joe Sestak and Patrick Murphy are challenging GOP Reps. Curt Weldon and Mike Fitzpatrick, respectively.

And from the Connecticut one:

A Lamont victory in the Aug. 8 primary could present another hurdle for Democrats Diane Farrell, Joe Courtney and Chris Murphy who are vying to oust GOP Reps. Christopher Shays, Rob Simmons and Nancy Johnson, respectively, in a state where Democrats have dominated in recent national elections.

That's at least three contests -- the races against Weldon, Shays, and Gerlach -- where the Netroots are going up against, or potentially going to impact, races where the unions are backing Republicans. Lois Murphy, who lost to the now union-backed Gerlach in Pennsylvania in 2004 and is challenging him again, was backed by Atrios, via ActBlue, to the tune of $15,727.89.

All of which raises an intriguing question: Can the Netroots make up for the defection of the unions to the Republican camp in these key races? So far they haven't developed a strategy to try, but if they did, I would think they could -- at least when it comes to fundraising. And maybe they should. It would certainly amplify their "party above interests" message and, if they could really make up the fundraising gap, it would endear them to party activists who increasingly see them as more interested in unwinnable statement races or knocking off conservative Democrats in primary contests (cough, Lieberman, cough) than targeting vulnerable Republicans. Most importantly, it just might help the Democrats retake the House.

Now, I'm not at all sure that the Netroots can make up for labor's GOTV efforts, since so many blog readers (and, presumably, donors) are based in places like California and lack the local networks and appropriate geographic placement to swing elections on the ground, but they have proven in at least two contests that they can provide enough money at crucial moments in campaigns to help Democrats succeed as well as to help mobilize out-of-state GOTV volunteers. Right now the Netroots vs. Unions dynamic seems to have sprung up somewhat by accident. Netroots leaders should seriously consider making it real by design.

--Garance Franke-Ruta