On a Friday night in late February, an endless line of families streams into San Jose’s St. Julie Billiart Catholic Church. By the time I take my seat towards the front, I’m looking out at a swelling crowd of more than 650 faces, participants in a prayer vigil in support of immigration reform. As people continue to squeeze into the church, and a live band strikes up a raucous version of Bob Dylan’s "The Times They Are a-Changin,’ " the electric energy brings to mind images of African-American churches in the South during the civil rights movement.

"Bastante gente," says a short and stocky man seated to my right, looking out at the crowd in amazement. Lots of people. I learn that he’s originally from the Mexican state of Oaxaca. "I’m here to support my daughter," he says, motioning to the girl beside him. Nancy Rodriguez Cruz, a 14-year-old high school freshman from the nearby town of Gilroy, is nervously fingering a note card and practicing her lines.

Thirty minutes later Nancy steps up to the microphone, following a woman who spoke movingly about her fear that her undocumented husband could be deported. By now, the audience includes the bishop of San Jose, Patrick McGrath, along with representatives from Democratic Congressmembers Mike Honda and Zoe Lofgren. As Nancy speaks, it becomes clear that while her father is here to support her, she’s also speaking up on his behalf.

"My parents are my heroes–I don’t know what I would do without them," she begins, her voice cracking in an effort to fight off tears. "Every morning I wake up terrified, thinking, ‘What if my parents aren’t home when I get back from school?’ Honestly, I don’t think a kid should be feeling that–they should be worried about their school problems and their homework. And if God gave me my parents, who is anyone to take them away from me?" After Nancy finishes her testimony the crowd breaks into loud applause, and when she returns to her seat she is met by her beaming father. "Very, very proud," he says.

In an age replete with Astroturf movements and manufactured media events, it’s unusual to come across a large political gathering without a member of the media in sight. In San Jose I saw no laptops or bloggers; I scoured the San Jose Mercury News the following morning without finding any mention of the vigil. Indeed, only Spanish-language media covered the event–one television channel, one radio station and a small bilingual newspaper.

But it’s this grassroots organizing–and there has been a lot of it in recent months–that holds the key to the passage of comprehensive immigration reform. The prayer vigil in San Jose was organized by People Acting in Community Together (PACT), just one of more than 750 groups that have joined the Reform Immigration for America coalition. "We have groups in almost every state," says Shuya Ohno, a coalition spokesperson. Since launching last June members have organized more than 1,500 actions and held hundreds of Congressional delegations. "But there are so many other groups doing things on their own," continues Ohno. "The amount of energy is incredible."

Not that it’s the first time that bustling grassroots activity has flown below the radar of major media outlets. In the spring of 2006, millions of immigrants took to the streets to protest a draconian piece of proposed legislation that would have turned all undocumented immigrants–and those who support them–into felons. The marches, which occurred in both major urban cities and anonymous rural towns, caught many by surprise. The groundswell of anger was covered and promoted heavily on Spanish-language radio, while mainstream outlets largely ignored it.

Something similar could be at work today, as immigrants and their allies mobilize from below. At this writing, organizers hope turnout for the immigration reform rally on March 21 in Washington, DC, could top 100,000, with unions, churches and community-based groups leading the way. Obama has come under fire from advocates who fault the administration for breaking its promise to move on reform in its first year and for escalating deportations. The prospect of the march caused the president to meet with senators Charles Schumer and Lindsey Graham, who have been drafting reform legislation, and to hold a special session with advocates, labor and church representatives. There’s a lesson here worth remembering: we didn’t put a community organizer in the White House–we put a former community organizer in the White House. Like any president, Obama will move on issues when groups force him into action.

It’s easy to see why conventional wisdom would argue against the likelihood of Congress passing immigration reform anytime soon. Obama’s critics point to the tortuous legislative process around healthcare to argue that he tried to do "too much"–despite the administration’s cautious and compromising approach to that issue. Meanwhile, the economy remains the central political concern, with official unemployment at nearly 10 percent. Yet there are plenty of realpolitik considerations that the push for reform has on its side–most obviously, there is the growing political clout of Latinos, who will certainly be paying attention to any political party that stands in the way.

As for jobs, plenty of recent analysis points to immigration reform as playing a positive role in jumpstarting an ailing economy. The Cato Institute, a libertarian think-tank, issued a report last year concluding that reform would add roughly $80 billion to the US economy per year. In January, a USC-sponsored report estimated that the state of California would take in an additional $16 billion annually by legalizing the state’s 1.8 million undocumented Latino adults.

It’s also important for the reform movement to move beyond statistics to tell stories that highlight the many benefits that immigrants bring to real places. I recently spent two months in Russellville, Alabama, a rural and extremely conservative town (for example, the sale of alcohol was prohibited). In recent years, thousands of immigrants from Mexico and Guatemala moved in–attracted by work in a poultry plant–bringing new life into a county that had seen its population steadily shrink. Vacant storefronts were cleaned up and reopened by immigrant entrepreneurs, the plant was able to secure a steady workforce and churches were bustling with bilingual services. "Latinos are responsible for most of the revitalization," the town librarian, Deborah Barnett, told me. "Before, everything was so deserted that we didn’t like having evening classes–it didn’t feel safe."

Conventional wisdom, too, can change quickly. Put 100,000 people on the ground in Washington, DC, for any issue, and elected officials and political journalists can start redefining what is politically possible. Representative Xavier Becerra framed the issue succinctly while speaking to hundreds of immigrants at a rally in Los Angeles. Becerra, who is a co-sponsor of the House reform bill introduced by Luis Gutierrez, told the restless crowd, "They don’t feel it in Washington, DC, the way you feel it."

But a large march by itself won’t deliver legalization for millions of undocumented immigrants. In organizing there is a saying: what’s important is what happens the day after an action. So the day after the march, members of PACT who are traveling to the capital will be meeting with politicians and handing over more than 20,000 signed postcards, calling for reform. As opposed to the marches in 2006, which were only loosely coordinated by unions, churches and community-based groups, this time around it feels more organized. Which is good, because when immigrants and advocates return home from what will hopefully be a large and successful march, the real work begins.