Massive fraud in voter registrations could conceivably help a candidate secure the White House. The price to our republic would be high.

In state after state, officials are discovering widespread problems with voter registrations obtained by the Association of Community Organizations for Reform Now (ACORN), a left-leaning activist group whose political-action committee backs Sen. Barack Obama. (That’s fine in itself. We like and admire Senator Obama.)

ACORN has received federal tax dollars to conduct its activities, and the Obama campaign gave $832,000 to an ACORN affiliate to get out the vote.

Officials in Michigan, Nevada, Ohio, Florida, New Mexico, North Carolina, Missouri, Wisconsin and other states are investigating ACORN registration activities. One 19-year-old Ohio man told The New York Post that ACORN activists had given him cash and cigarettes in exchange for his registering 72 times. Fictitious or stolen names, including cartoon characters and the members of the Dallas Cowboy football team, fraudulent addresses and false Social Security numbers have turned up in voter registrations.

The danger of such registrations, of course, is that people could vote illegally — illegal aliens, ex-convicts denied the vote, or simply the same person voting multiple times under different registered names, canceling out legitimate votes. Interestingly, too, many pollsters base their snapshots on changes in registration data; thus, a dramatic increase in Democratic registrations (fraudulent or not) would cause them to sample that many more Democrats than Republicans, which could tilt polls. Senator Obama said it is unlikely that anyone would exploit fraudulent registration records to cast actual votes. But he knows that’s not true. Of course such fraud will take place, as it has taken place in the past, perpetrated by Republicans, Democrats and others.

Two prominent former senators, John Danforth and Warren Rudman, moderate Republicans who back Sen. John McCain, warned of a “potential nightmare” on Election Day unless the monitoring of the polls is stepped up, particularly in “battleground states,” where the election results are expected to be close. The problem, though, may be most acute with absentee voting, a growing practice that could be particularly susceptible to fraud since no one is watching the person vote. The senators advised that, for starters, Senator Obama should ask ACORN to stop employing people with criminal records to register voters. Senator Obama, for his part, says that, while he once worked as a lawyer for ACORN, he has nothing directly to do with the organization.

Meanwhile, the Justice Department should investigate whether this is part of a systematic attempt at voter fraud. And states should step up efforts to identify fraudulent registrations.

Finally, states should move to implement such sensible precautions as a photo ID requirement for voting — as we have for driver’s licenses. Some say this would disenfranchise poor and elderly voters, since they would tend to find it more difficult to obtain an ID. But steps can be taken to help such voters. It is important to make sure that legitimate voters are not effectively disenfranchised by political skulduggery.