CNBC editor Rick Santelli's on-air "rant" in February 2009 about a proposed mortgage bailout is widely considered to be the "big bang" moment for the birth of the movement.
A few days later, a couple of conservative foot soldiers – John O'Hara of the Heartland Institute and J.P. Freire, then of The American Spectator – wondered if there were a way to harness Mr. Santelli's frustration.
"You know what would be funny?" Mr. Freire mused to Mr. O'Hara, leading into a discussion that would become so much more than talk.
The pair organized "A New American Tea Party" rally outside the White House on Feb. 27, according to O'Hara's book about the movement. Six weeks later (around tax day), about 500,000 people took to the streets in small, medium, and large protests from San Francisco to Atlanta. Today, says O'Hara in a phone interview, "there are absolutely hundreds" of local and state tea party organizations.
[Editor's note: This is an updated version of a story that first ran on Feb. 4]