“I was very disappointed because I put so much work into it,” Ms. Norman, 42, a model for art classes, said this week in a telephone interview. “And so did some other people. But we were the only ones there. The secular community as a whole seemed so indifferent. It wasn’t like nobody knew. It was like nobody cared.”

Ms. Norman’s exasperating effort to mobilize nonbelievers as a political constituency was not some local anomaly. The difficulty of delivering secular voters in the way numerous religious groups are routinely and effectively put into electoral action reflects a national trend.

While a bold brand of in-your-face atheism may be enjoying great success in the marketplace — as witness the popular books by Mr. Dawkins, Sam Harris and Christopher Hitchens, as well as Bill Maher’s new satiric documentary “Religulous” — no similar impact has been evident in politics.

Only one of the 535 members of Congress, Representative Pete Stark, Democrat of California, publicly identifies as a nontheist, according to the Secular Coalition of America, a lobbying group based in Washington. For that matter, the coalition has existed for only three years and runs with two staff members and an annual budget of about $300,000. As both presidential candidates ardently court religious voters, atheist support is considered so controversial that several Democrats writing on the atheist blog Petty Larseny quipped that the best way to hurt the Republicans was to form a group called Atheists for McCain.

“We are where gays were at the time of Stonewall,” said Lori Lipman Brown, the director of the Secular Coalition, referring to the 1969 riot in Greenwich Village that was the birth of the gay rights movement. “And the thing we have in common with gays back then is that day to day you’re hidden. If you make the decision to come out, you’re treated very badly.”

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“We should have a base of at least 30 million Americans to work with,” Ms. Brown continued. “And yet those who are active are a much smaller percentage. We’re probably looking at just a few hundred thousand active participants. It’s hard to even quantify.”

The situation in Colorado offers a case history of some particular obstacles to organizing the secular constituency.

Amendment 48 is exactly the kind of starkly drawn measure that political consultants refer to as an “emotional trigger” for prospective voters. Yet such a ballot item also demands the tactile, personal campaigning known in the trade as “retail politics.” A voter in Colorado this year faces 14 ballot initiatives as well as choices for president, senator and representative, and it will take no small amount of motivation and training to find, much less vote on, Amendment 48.

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Polls since the summer have shown the amendment trailing, with about 40 percent of likely voters in favor, about 50 percent opposed and about 10 percent undecided. While the umbrella group for the amendment’s foes, the No On 48 coalition, includes some secular organizations, many of its most active volunteers come from issue-based organizations like Planned Parenthood or liberal religious denominations like mainline Protestants and Reform Jews.

One problem with turning out the atheist vote is finding it. Atheists do not reside visibly in certain neighborhoods like blacks or Hispanics or gay men and lesbians. They do not turn up on the databases of professional associations like doctors or lawyers. And as nonbelievers, they axiomatically do not come together for worship.

“It’s harder for them to organize,” said Brian Graves, 27, an organizer for No On 48, “because they don’t have something to congregate around.”

With their trust in the power of reason, atheists might also be ill-equipped for the gritty work of retail politics — the phone banks, the door-knocking, the car pools to the polls. If nothing else, they are coming late to the craft.

As founder and leader of a Colorado-based coalition for secular government, Diana Hsieh has written a detailed position paper attacking Amendment 48. Other atheist activists have written letters to the editor and participated in online forums about the ballot measure. Relatively few, however, have thrown themselves into the get-out-the-vote operations that conservative Christians, for instance, have excelled at.

“We need to get more of our people out,” said Ms. Hsieh, 33, a doctoral candidate in philosophy at the University of Colorado. “It’s just not the strategy I’ve taken. I’m a policy-wonk type. Going to talk to people outside the grocery store is just not going to be my strong suit.”