No. Because they are the biggest buyers of influence on the hill. It has absolutely nothing to do with having a bunch of people, just a bunch of money.
Sorry, but that's like looking at Hawaii and saying the US is a tropical country. You're ignoring 90% of the money spent by organizations to influence Congress.
Donations are only one small way that money influences the hill. If they were as effective as lobbying, you wouldn't see 10X the money being spent on that.
To me, any concentration of power, whether unions, corporations, etc. is dangerous to democracy. These people each voting their own mind is one thing, but these orgs encourage zombie voters that always vote the same way - while having central leaders to play / pay hard. This is very different from politicians just looking out for their voters.
Concentration of power via voting groups is a fundamental part of the democratic process, be it via representatives creating factions within legislatures or voters banding together to create political groups. (In the end, the Democratic and Republican party are essentially that.) Doing so allows smaller factions that have a single driving issue to have some political impact by focusing their voting behavior on that one axis.
