Grant funds are not the biggest factor in this, IMO. The Gov is not a great source of grant funds to liberal groups. EPI had some expectations of better treatment in this dimension and was totally disappointed after 1992. We were told that giving us grant money would reflect badly on the Administration, since we had helped in the election campaign.
More important is the prospect of Administration positions and the consummation of pragmatic deals between constituency groups and the new Administration. An Administration position is not all that well-paid, except compared to normal people, but it leads to very big bucks (i.e., $150K plus) later on with a consulting firm or trade association.
Most important, I would say, is the political implications of someone less liberal being outflanked by someone more liberal, especially when 'more liberal' is well short of socialist or something easily marginalized. Nader's unradicalism enrages people. You think your politics makes you special, and someone else shows you up as ordinary. For someone leading a constituency organization, Nader of course calls one's political strategy and competence into question. There is competition for leadership in many of these organizations.
For intellectuals, one's vision is brought into question. Maybe this is the unkindest cut of all. Take my committed, dedicated friend Nathan. For all his Herculean activist labors, when it comes to policy, he just isn't all that radical. And I say this in light of the fact that I don't think I'm all that radical myself (and w/much less activist background than NN). I think radical is properly defined not as what you think would be ideal, but what you are unwilling to surrender as a matter of practice. To what are you willing to say 'no'? I say no to Al Gore. I don't think that's so radical.
mbs