Anyone skeptical about the power of incumbency and committee assignments need look no further than Randy Kuhl's recent campaign finance report. Kuhl, who withdrew his co-sponsorship of H R 800, the Employee Free Choice Act, called the bill "Orwellian", and was confronted by 150 union members after a town meeting, received $2,500 from labor PACs in the first quarter of 2007.
Kuhl, who received a "Spirit of Enterprise" award from the U.S. Chamber of Commerce for his 100% voting score last year, wasn't endorsed by the AFL-CIO in 2006, yet he received $500 from the AFL-CIO Transportation Trades Department PAC. He also received $1000 each from the firefighters and iron workers.
I suppose the labor unions think they're getting something out of their contributions: presumably their donations are related to Kuhl's committee assignments in the Transportation and Infrastructure or Education Committees (since it was the Firefighters "Registration and Education" association that contributed). Maybe their $500 or $1000 bought a few minutes of face time, or they hope it will result in a call that's returned.
That said, I wonder how they would explain their contributions to the 150 union members who showed up in Corning a couple of weeks ago.