The difference is really the level of popular support. Even Graham and Santorum, who weren't even on the "main stage" of the recent GOP debate, have won U.S. Senate elections and have national name recognition that far outstrips Lessig.

Lessig seems to think that if he eked his way onto the stage of a televised Democratic debate, he'd have a chance of jump-starting a national political campaign on the issue of campaign finance.

But it's actually the reverse: you only get onto a debate stage if you already have a campaign. The polling criteria is not a gotcha. It's just the easiest way to ensure that only people with actual popular traction get stage time. The debate is not intended to be a "big intro" opportunity. There are other events for that, like the convention (Obama), or big events like the Prayer Breakfast (Ben Carson).

In part the difference in the numbers between the parties is simply that there is no clear favorite on the GOP side, while there is an overwhelming favorite on the Dem side. There are a lot of senior Democrats who have chosen to sit this one out rather than challenge Hillary.