During this country's last presidential election, 20 million single women did not vote.

Women's Voices, Women Vote, a nonprofit in Washington, D.C., is trying to reach those women and persuade them to cast ballots this year and in 2008. Reaching these voters is difficult, said Joe Goode, executive director of the group.

"Fifty percent of these single women live in households that make less than $30,000 a year. They are very economically depressed," Goode said.

Those 20 million single women, he added, "make up about 24 percent of the voting age population. But in the 2004 election, they were only 22 percent of the people who actually voted."

By contrast, Mr. Goode said, "married women comprise 28 percent of the voting population, but their participation was 31 percent in the last presidential."

The 20 million figure, a projection by the U.S. Census Bureau, is based on a population survey conducted after 2004.

"When people hear it, they're like, 'How can that be?' We aren't even talking about the married women who don't vote. We focused on single women because we felt it was a targetable demographic," he added.

Women's Voices, Women Vote refers potential voters to Web sites such as www.ontheissues.org, so they can learn about various political topics, and also it mails them absentee ballots.

Many voters justify their failure to participate by saying, "I don't know enough to vote. Therefore, I don't vote," Mr. Goode said.

"The second big reason is they get tired of negative campaigning and the partisan nature of everything. They don't know who to trust."

Many single women "may be struggling just to get ahead. They may be single moms. So their support network just isn't the same as married women who tend to be upper income and a little more established in terms of where they live."

One reason for this disparity, Mr. Goode suggests, is that "single women tend to be more mobile. A third of them move every two years or less. They might not even know where to go to vote. A lot of them are under 30 and a lot of them are over 60."

Whatever their age, these are women with concerns about affordable health care, the cost of education and pay equity.

Sara Grove, a professor who holds the Elsie Hillman Chair in politics at Chatham, understands the large burdens many students shoulder today.

"If you are attending college ... this is one of the last things you are paying attention to," Ms. Grove said, adding that many students carry 12 college credits so they can obtain health care benefits while also working a full-time job. They wind up struggling to stay afloat academically and financially.

"That is increasingly becoming the dilemma more and more students face," Ms. Grove said. There has been "no effort in the General Assembly to provide student loan money. The issues that are being discussed aren't issues women are worried about in their everyday lives. ...

"There is a lack of understanding by some of what it's like to be a single mother, trying to make ends meet and trying to address how we can improve that woman's status. You don't see many single women being successful and winning public office."

Barbara DiTullio, program manager for WomenVote PA, said Pennsylvania is the only state in the nation where women are less likely than men to be registered to vote. One way to draw more women to the polls, she said, is to hold elections on weekends.

"Why does it have to be on a Tuesday between 7 a.m. and 8 p.m. when people are working and children are in school? If we really want to engage people, we have to make it easier for them to vote."