Nah, I don't see it this way. Dems get money from Liberal groups, mind you, but their real issue is getting people elected. I believe devoutly that they decide based upon their hold on a state who is going to take a "stand".
Look at Kerry's election-year votes on the war. Those weren't Kerry's concience, those were the votes of someone whose seat isn't going to a Republican any time soon, and someone who needed to boost their standing as a liberal in the face of Dean. On all these "touchy" issues, Democrats pick a token few legislators to make the unpopular vote, and they aren't going to pick someone who is going to suffer for it. Hell, Kerry voted against the GULF war. EVEN THEN someone had to be the token muckraker.
I think if you want to blame anyone for pandering to Liberal interest groups, blame the party as a whole. They know Roberts is going to go in, they just need to make a statement for fundraisers, and want it to do the least amount of damage possible. They also want it to be someone who needs a bit of the gloss put back on their Left status.
Reid got twice as many votes as his opponent in 2000. He's wishy-washy as hell on liberal issues (NARAL gave him a 20 something percent rating). This brings him up in the eyes of wary Libs, and gives the impression some Dems "fought the good fight" against Roberts. He gets to continue being conservative on Abortion, but appear to be fighting for women's rights.
I agree that it is pandering, but I think you have to see it as an overall strategy by the party itself.