Jon Stewart and Stephen Colbert’s dueling rallies are shaping up to be truly massive.

Sign-ups for the rally have been tallied on Facebook. Beyond the 290,000 who have so far signed on as definite attendees, 145,000 more have listed themselves as maybes.

The site rallymao.com has assembled a roster of the scheduled satellite events in more than 25 states. One in New York City has been set for the SoHo Gallery for Digital Art. Other sites include the Capitol Rotunda in St. Paul, Civic Center Park in Denver, Manuel’s Tavern in Atlanta and Wasilla Middle School in Alaska.

The international locations so far include London, Paris and Melbourne (no specific sites mentioned), along with the Copenhagen Town Hall in Denmark and, perhaps most intriguingly, “base camp” at Mt. Everest in Nepal.

Mr. Stewart and Mr. Colbert have so far offered few specifics on the event. Mr. Colbert’s blowhard-conservative character will try to counter Mr. Stewart’s message — seeking a more rational approach to political discourse — by urging participants to “keep fear alive.”

But the Rallymao site made an attempt to characterize the event: “It’s like Woodstock, except it’s going to be everywhere, and without the mud.”

Groovy.