WASHINGTON — In 2006, conservative activists repeatedly claimed that the problem of people casting fraudulent votes was so widespread that it was corrupting the political process and possibly costing their candidates victories.
The accusations turned out to be largely false, but they led to a heated debate, with voting rights groups claiming that the accusations were crippling voter registration drives and reducing turnout.
That debate is flaring anew.
Tea Party members have started challenging voter registration applications and have announced plans to question individual voters at the polls whom they suspect of being ineligible.
In response, liberal groups and voting rights advocates are sounding an alarm, claiming that such strategies are scare tactics intended to suppress minority and poor voters.
In St. Paul, organizers from the Tea Party and related groups announced this week that they were offering a $500 reward for anyone who turned in someone who was successfully prosecuted for voter fraud.
The group is also organizing volunteer “surveillance squads” to photograph and videotape what it suspects are irregularities, and in some cases to follow buses that take voters to the polls.
In Milwaukee last week, several community groups protested the posting of large billboards throughout the city that show pictures of people behind jail bars under the words “We Voted Illegally.” The protesters said the posters — it was not clear who paid for them — were intended to intimidate people from voting.
In Houston, a Tea Party group called the King Street Patriots recently accused a voter registration group, Houston Votes, of turning in voter registration applications with incorrect information.
Voting rights advocates say they are worried.
“Private efforts to police the polls create a real risk of vote suppression, regardless of their intent,” said Wendy R. Weiser, director of the Voting Rights and Elections Project at the Brennan Center for Justice at New York University. “People need to know that any form of discrimination, intimidation or challenge to voters without adequate basis is illegal or improper.”
Voter fraud and voter-registration fraud are, of course, different.
While many states have voter registration records riddled with names of dead people, out-of-date addresses and other erroneous information, there is little evidence that such errors lead to fraudulent votes, many experts note.
A report by the public-integrity section of the Justice Department found that from October 2002 to September 2005, the department charged 95 people with “election fraud”; 55 were convicted.
Among those, fewer than 20 people were convicted of casting fraudulent ballots, and only 5 were convicted of registration fraud. Most of the rest were charged with other voting violations, including a scheme meant to help Republicans by blocking the phone lines used by two voting groups that were arranging rides to get voters to the polls.
Even so, the fear of stolen votes remains, as does the fear of missing votes — particularly in light of a decrease, compared with 2006, in voter-registration applications in swing states.
About 43 percent fewer new voters have registered in Wisconsin this year than in 2006, while in Indiana, the decrease has been about 35 percent. Significant drops have also been seen in Ohio (25 percent), North Carolina (28 percent), Florida (27 percent) and Maryland (21 percent), according to state election data collected by the Brennan Center.
Voting experts say several factors explain the trend.
Voter enthusiasm is low now, and fewer groups like the Association of Community Organizations for Reform Now, or Acorn, are engaged in drives to sign people up. Acorn collected about 550,000 voter-registration applications across the country in 2006, mostly from low-income and minority Americans, and 1.3 million in 2008.
But in March, the organization closed down after accusations by two conservative activists that low-level Acorn employees had advised them on how to hide prostitution activities and avoid taxes. The group was also battered by conservatives for having submitted some voter registration cards with incorrect, duplicate or false information.
The housing crisis may also have dampened voter registration. More than three million properties were foreclosed this year, a 30 percent increase from 2008, and people who have been forced out of their homes may be not be able establish residency to vote.
Many states have also enacted laws in recent years that make registration drives more difficult, with stricter reporting and filing deadlines for voter registration groups.
“It has been an uphill fight in a lot of states to register people this year,” said Elisabeth MacNamara, national president of the League of Women Voters.
Ms. MacNamara said the group’s Georgia chapter faced an additional burden because of a new state law requiring voters to prove citizenship. The chapter does not have a copier machine, so the expense of duplicating documents like birth certificates or driver’s licenses falls to unpaid volunteers.
Most of the new barriers to registration are likely to hurt Democrats more than Republicans. Historically, these registration drives have focused on voters in poorer areas and minority communities, which tend to vote Democratic.
The Obama administration has tried to take steps to lessen the dependence on independent voter registration groups, while also broadening voter participation among poorer and minority voters.
In June, the Justice Department released new guidelines for the “motor voter” law, emphasizing that all public-assistance applicants must be given the opportunity to register to vote, and that state employees must offer to help them.
Still, independent voter registration groups say that they still play an important role, and that scare tactics are making their work harder.
“There is an intentional effort here to suppress participation,” said Jim George, a lawyer for the Texans Together Education Fund, the parent organization of Houston Votes.
Houston Votes, whose registration drive has mostly focused on Latino neighborhoods, did find at least one paid canvasser submitting fraudulent applications, Mr. George said, and that person was immediately fired. He added that the groups’ financing for voter registration work had dried up because of insinuations by the King Street Patriots that Houston Votes was tied to the New Black Panther Party.
“Houston Votes has nothing whatsoever to do with the Black Panthers,” Mr. George said. “But you make a claim like that, and funding dries up, even if the claim isn’t true.”
Mr. George explained that during a meeting, the King Street Patriots had shown a picture of the Houston Votes office and stated its address before adding that this was the new location of the Black Panthers.
Hiram Sasser, a lawyer for the Liberty Institute who represents the King Street Patriots, denied the claim but when presented a video of the incident, he said that his client had actually made a mistake and did not realize the office was tied to Houston Votes.
Leo Vasquez, the Republican tax assessor-collector and voter registrar in Harris County, Tex., which includes Houston, said that of about 25,640 registration applications submitted by Houston Votes, about 5,500 had problems.
The Texas Democratic Party has filed a lawsuit against Mr. Vasquez, accusing him and the voter registration office of illegally rejecting voter applications.
The fight occurs against the backdrop of a contest for governor in which a large turnout in Harris County would be vital to the effort by the Democratic candidate, Bill White, to defeat Gov. Rick Perry, a Republican.