Amy Kremer had an "empty space" in her life; she filled it by co-leading an insurrection that has rocked American politics

Less than two years ago, Amy Kremer and Jenny Beth Martin were 30-something suburbanites in metro Atlanta, frustrated by recession, dismayed by the election of Barack Obama and waiting for the next chapter of their lives.

Ms. Kremer, a former Delta Air Lines flight attendant, had quit her career to raise her daughter. The child had grown up and just moved out, and now Ms. Kremer was filling her time with two blogs—one on gardening, one on politics.

"I had this empty space in my life," Ms. Kremer recalls.

Ms. Martin, a software manager by training and part-time blogger, was cleaning houses to help pay the bills after her husband's temporary-staffing business collapsed. They were in danger of losing their home.

As her family's fortunes crumbled, Congress—including Sen. Saxby Chambliss (R-Ga.), for whose campaign Ms. Martin had volunteered—voted for President George Bush's bill to bail out the big Wall Street banks.

Ms. Martin was enraged. "It wasn't because the government didn't bail my husband's business out," she says. "Sometimes it stinks when your business goes bad. But it's part of our system.… The government doesn't need to come in and hold a business up and keep it from failing."

In the span of a few weeks in February and March 2009, the two women met on a conference call and helped found the first major national organization in the tea-party movement. Within months, they became two of the central figures in the most dynamic force in American politics this year.

Ms. Kremer, 39, currently chairs the political action committee known as the Tea Party Express. It has raised millions of dollars for upstart candidates and engineered the campaign that threatens Senate Majority Leader Harry Reid (D-Nev.). Once shy about public speaking, today she crisscrosses the country addressing thousands at a time. "Are you ready to fire Harry Reid?" Ms. Kremer bellowed to a crowd of 2,000 in Reno, Nev., this month.

Ms. Martin, 40, is national coordinator of the Tea Party Patriots, an umbrella group claiming affiliation with nearly 3,000 local groups around the U.S. Leaving her young son and daughter at home, she is on a 30-city tour, revving up activists for the victory she is counting on next Tuesday.

"This was something I had to do," Ms. Martin says. "There were just so many of us who were fed up with the Republican Party."