It seems clear the Promise Keeper organization is on the verge of pulling off one of the single largest religious gatherings in American history.
What is unclear is if it will have any larger resonance beyond the experiences of those who participate.
The site of this weekend's march, the Mall in Washington, has been the venue for some of the nation's most visible protests dating back before the turn of the century.
But experts say their ability to impact America, and make the history books, is based less on their size than on the receptivity of the public to the message the groups are trying to convey. Marches that seem to sum up the nation's feelings or desire for social change are usually the most successful.
"Sometimes you think of these marches, and they reshape American history," says Harry Rubenstein, a political historian at the Smithsonian Institution. "They fall into a historical context. They are capstones that serve to solidify and acknowledge public opinion."
One of the earliest and most successful rallies, for instance, was the 1913 suffrage protest. Some 10,000 women marched down Constitution Avenue in hopes of winning their gender the right to vote. Troops were called in to quell violence caused by well-wishers - mainly men - still in town for Woodrow Wilson's inauguration. Despite the harshness of the day, the women garnered increasing public support for their cause.
More recently, the 1963 March on Washington by blacks, which culminated in Martin Luther King Jr.'s "I Have a Dream" speech, focused national attention on the plight of minorities and helped spur passage of the landmark Civil Rights Act of 1964.
But not all rallies reshape public attitudes. Mr. Rubenstein points to some of the labor marches of the 1980s as beginning and ending "at that moment" because national sentiment was not on their side at the time.
The frequency of marches in the 1980s and '90s has also diluted the impact of some protests. Nevertheless, depending on the message and the group, rallies like this Saturday's "Stand in the Gap: A Sacred Assembly for Men" can still become seminal events, touching the lives of millions of Americans.
"A protest has many audiences: the public at large, the government, the people who are there themselves, and the fourth is a specialized public," says Kay Schlozman, a political scientist at Boston College. She calls the specialized public those sympathetic to the message or cause - in this case, men searching for stability in their family lives who are also receptive to church.
An estimated 650,000 to 1 million men are expected to converge on Washington to attend the "Stand the Gap" rally. They will listen to speakers, pray, commit themselves to strengthening their families and churches, and pledge marital fidelity.
Even though women's groups have criticized the organization's conservative views, sponsors predict the rally will resonate far and wide. Others are more measured.
"This is a very difficult time because the traditional roles of what it means to be a woman and a wife and a husband and a father are undergoing great change," says John Green, a religion scholar at the University of Akron in Ohio. "Promise Keepers offers some pretty good answers to that, but they are traditional answers."
The event could strengthen the organization's standing among conservative Christians. But the group's message and mission is too traditional to galvanize a wider audience, some say. "People are looking for direction, and churches play a role," says Richard Celente, author of "Trends 2000." "But there is a large part of the [baby] boomer population that doesn't want anything to do with church."
"The question is this going to be a comet? Life goes on, the comet fades, and we turn attention elsewhere," says Ms. Schlozman. "It is the organization that keeps the effort going."
Some believe the Promise Keeper movement may have peaked. They note the number of people attending stadium events, the normal Promise Keeper venue, have declined this year. But others point out that many men have bypassed the stadium conclaves to wait for the Washington rally.