Epicurus
Reasonable
Comparisons to the left don't really work. There is no one on the left who has had the kind of consistent influence & following that Limbaugh has had on the right, for 20 years now. Limbaugh is like an elder statesman at this point.
Also, no pundits really "lead" the Dem party at the moment, because Democrats - and I'm not saying this is always the case - have a pretty clear message & agenda they are putting out there. The GOP is lost at the moment, and Rush is filling the void. I think a good argument can be made that he is leading the party more than any other, at least right now.
I can agree with part of this. I will at least say that informal leadership of the Democratic Party is more diversified. There is not a direct equivalent of Rush on the left, but instead more individuals who command personal influence. Keith Olberman, Paul Krugman, Jon Stewart, Chris Matthews, Bill Maher, and Al Franken to name a few.
Where the Democratic Party is shamefully subservient is its dealings with groups like Moveon. After the vote to denounce the "Betray Us" ad, many Democratic legislators had to go and beg forgiveness at that alter as well.