Of all the political activists in this city, Jim Cronin might be the most unlikely.

An ex-convict who has been homeless since 1994 -- and a self-described "horrendous drunk" for most of his life -- Cronin, 65, had an epiphany a few months back while talking with another guest at the Pine Street Inn, a Boston shelter, about the importance of voting.

Within days, Cronin and his friend Fred Atkinson began encouraging their fellow guests to register to vote. Since then, the two men have visited dozens of Massachusetts shelters to sign up more than 400 homeless men and women.

"The condition of being homeless is always feeling 'less than' or 'not a part of.' I know voting helps them, because of how it has helped me feel like I belong," Cronin said. "This is an election year, and it's like living in the shadows if you're not part of the process."

On Thursday, Cronin and Atkinson took their idea national, as shelters in 16 states and the District joined in what organizers called the first-ever National Low Income and Homeless Voter Registration Day. The two men contacted several shelters and homeless advocacy groups who began to plan the registrations.

The initiative, timed to coincide with the Democratic National Convention, was supposed to be nonpartisan.

"The lower income bracket has the worst voter turnout of any income bracket, so their voices aren't being heard," said Michelle Laslov, social justice coordinator for So Others Might Eat, which provides food, clothing and health care to the homeless and poor at its headquarters on O Street in Northwest Washington. Staff members and a group of formerly homeless volunteers distributed registration forms during Thursday's lunch.

In Boston, where an estimated 6,000 homeless people live, Cronin, Atkinson and a group of homeless or formerly homeless volunteers gathered outside the Mary Baker Eddy Library for the Betterment of Humanity and registered about 170 voters. Volunteers helped usher people off shuttles run by various shelters, assisted them with filling out registration forms and handed out yellow buttons that read "Registered Voter."

"You can speak and yell as loud as you want, but you will not be heard until you register to vote," said Boston Mayor Thomas M. Menino (D).

Cheri McCulley, 34, has been homeless for about a month, along with her three children, said she has never voted. But when she saw a flier posted in the Women's Hope Transitional Home, in Dorchester, Mass., she knew the time had come.

"I never cared much about voting one way or the other until I ended up in this situation," she said. "I'll support anyone with a program to help people get out of shelters and back into the real world."

Cheryl Jackson, an intern for the National Low Income Housing Coalition, which helped coordinate Thursday's drive, said there is more than just self-esteem at stake for the estimated 2.3 million to 3.5 million Americans likely to experience homelessness in any given year.

"There are issues on the table right now across the country that are going to significantly affect these voters," Jackson said. "We tell them that civic participation is one of the ways they can change their status."