In Wednesday night’s debate, John McCain warned that a group called Acorn is “on the verge of maybe perpetrating one of the greatest frauds in voter history” and “may be destroying the fabric of democracy.” Viewers may have been wondering what Mr. McCain was talking about. So were we.

Acorn is a nonprofit group that advocates for low- and moderate-income people and has mounted a major voter-registration drive this year. Acorn says that it has paid more than 8,000 canvassers who have registered about 1.3 million new voters, many of them poor people and members of racial minorities.

In recent weeks, the McCain campaign has accused the group of perpetrating voter fraud by intentionally submitting invalid registration forms, including some with fictional names like Mickey Mouse and others for voters who are already registered.

Based on the information that has come to light so far, the charges appear to be wildly overblown — and intended to hobble Acorn’s efforts.

The group concedes that some of its hired canvassers have turned in tainted forms, although they say the ones with phony names constitute no more than 1 percent of the total turned in. The group also says it reviews all of the registration forms that come in. Before delivering the forms to elections offices, its supervisors flag any that appear to have problems.

According to Acorn, most of the forms that are now causing controversy are ones that it flagged and that unsympathetic election officials then publicized.

Acorn’s critics charge that it is creating phony registrations that ineligible voters could use to cast ballots or that a single voter could use to vote multiple times.

Acorn needs to provide more precise figures about problem forms and needs to do a better job of choosing its canvassers.

But for all of the McCain campaign’s manufactured fury about vote theft (and similar claims from the Republican Party over the years) there is virtually no evidence — anywhere in the country, going back many elections — of people showing up at the polls and voting when they are not entitled to.

Meanwhile, Republicans aren’t saying anything about another more serious voter-registration scandal: the fact that about one-third of eligible voters are not registered. The racial gaps are significant and particularly disturbing. According to a study by Project Vote, a voting-rights group, in 2006, 71 percent of eligible whites were registered, compared with 61 percent of blacks, 54 percent of Latinos and 49 percent of Asian-Americans.

Much of the blame for this lies with overly restrictive registration rules. Earlier this year, the League of Women Voters halted its registration drive in Florida after the state imposed onerous new requirements.

The answer is for government to do a better job of registering people to vote. That way there would be less need to rely on private registration drives, largely being conducted by well-meaning private organizations that use low-paid workers. Federal and state governments should do their own large-scale registration drives staffed by experienced election officials. Even better, Congress and the states should adopt election-day registration, which would make such drives unnecessary.

The real threats to the fabric of democracy are the unreasonable barriers that stand in the way of eligible voters casting ballots.