By Thomas Ferraro

WASHINGTON, Oct 24 (Reuters) - Felons could account for up to 10 percent of the roughly 130 million Americans expected to vote in the Nov. 6 election, more than enough to affect the razor-thin margins that could determine the outcome.

But as in years past, neither Democrats nor Republicans are doing much to reach out to them.

"Criminals are not a popular constituency," says James Hamm, 64, who spent 17 years in prison in Arizona for a drug-related homicide and now heads an inmate advocacy group with his wife, a retired judge. "Politicians don't want to say, 'Hey, I have the backing of people who committed crimes.'"

Still, both presidential campaigns have reason to be attentive to the estimated 13.4 million felons who are eligible to vote.

Felons traditionally vote Democratic, says Christopher Uggen, a University of Minnesota sociologist, who co-authored a 2006 book, "Locked Out: Felony Disenfranchisement and American Democracy."

That is because felons come disproportionately from groups that align with Democrats, such as minorities, the poor and urban residents. In this group, Uggen says, "you aren't going to find too many Mitt Romney supporters."

A 2010 study that Uggen participated in found that just one in five felons who are eligible to vote actually do so, most mistakenly believing they are not. Myriad state laws that take different approaches to restoring felons' voting rights contribute to the confusion.

There are an estimated 20 million felons in the United States, including 1.5 million now in prison, according to statistics provided by Uggen. About 5.6 million of them are forbidden to vote by state laws. Depending on where they were convicted, the other 13.4 million have either had their voting rights restored or never lost them, even when incarcerated.

While campaigns generally steer clear of convicted criminals, the Obama camp has reached out to them in at least one place, the undecided hotbed of Ohio. The only felons in the state prohibited from voting are those behind bars on Election Day.

Ohio has an estimated 784,0000 felons, 52,000 of them in prison. The others are on probation, out on parole, or have finished their sentences.

Neither Obama nor Romney campaign spokespeople replied to repeated requests for comment about efforts to get out the felon vote.

Nancy Abudu, senior staff counsel with the American Civil Liberties Union's Voting Rights Project, said felons "face a lot of roadblocks and discrimination in trying to exercise their right to vote."

"The states haven't done a good job telling people when their rights have been restored," Abudu said, adding that officials themselves are often confused about the law.

In 38 states, most felons automatically regain the right to vote once they complete their sentences, according to the National Conference of State Legislatures.

Felons in others states must not only complete their sentences but wait a certain amount of time before they can again cast ballots.

In Maine and Vermont, felons never forfeit their right to vote. In Florida, Iowa, Kentucky and Virginia, felons are barred from voting unless the governor decides otherwise.

In 2007, then-governor of Florida Charlie Crist, a Republican, allowed nonviolent first offenders to get their voting rights restored automatically upon release from prison. He subjected others to a review.

Four years later the state's Republican Governor Rick Scott ended Crist's reforms and imposed tough hurdles, including a waiting period of five to seven years (depending upon the crime) after completion of a sentence before felons can even apply for restoration.

Civil rights groups oppose the change.

"Studies show that the recidivism rate for felons goes down significantly when they are given back their basic civil rights, including the right to vote," said Ron Bilbao of the ACLU in Florida. "The governor went in the wrong direction."

Marc Mauer, executive director of the Sentencing Project, a nonprofit advocacy group for criminal justice, said ex-inmates are generally ignored when it comes to voting.

"There simply isn't a lot of encouragement for them to even register," said Mauer. "If we believe everyone should vote, we shouldn't put character conditions on it."

Betty Smithey, 70, was released from prison in Arizona in August after spending 49 years behind bars for murder. An Obama supporter, she said she looks forward to voting for the first time: "It makes me feel like I'm back in the human race." 

(Additional reporting by Jeff Mason)

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