On Election Day 2000, tens of thousands of Floridians accidentally marked their ballots in ways that could not be read by the state’s voting machines. Their votes didn’t count. The identity of our next president hung in the balance for 36 days.

To prevent the Florida debacle from repeating, Congress passed the Help America Vote Act in 2002. The law required states to upgrade their voting machines. Voting machines must now warn voters and give them an opportunity to correct their ballot if they determined there was an “overvote,” the invalid selection of more than one candidate, on the ballot.

This technological fix was supposed to make these kinds of lost votes a thing of the past. Although there is no reliable nationwide data on the number of overvotes in recent elections, it is likely that the voting-machine changes mandated by HAVA have substantially reduced overvoting.

But the HAVA requirements haven’t been enough to prevent votes from being lost — sometimes in staggering numbers — in recent elections. There were 60,000 lost votes in New York’s 2010 general election. Several counties in Ohio saw more than one in every 200 votes for governor voided as overvotes in 2010. The problem has even reared its ugly head again in Florida. In just 13 Florida counties in 2008, 17,500 votes for president were discarded as overvotes; advocates blamed inadequate overvote protections on the voting systems in those counties.

We often see these kinds of lost votes in poor urban communities: In East St. Louis County, Ill., 1.37 percent of all votes for president didn’t count in 2008. But rural communities are also affected: In Chicot County, Ark., 1.36 percent of all votes cast for president were not counted in 2008.

Part of the problem in these locations has been that when voting machines give voters the opportunity to correct their invalid ballots, the message shown on the screen is extremely confusing. In Florida and New York, for instance, the message told voters only that they had “overvoted” without telling them what that meant or that their votes would not count if the ballot wasn’t corrected.

But even a clearer warning message will not entirely prevent lost votes. As long as machines accept overvoted ballots, citizens will continue to lose their votes. There is an obvious solution, of course: Voting machines can automatically reject overvoted ballots, forcing the voter to correct them. This is done in many states, including California, New Mexico, Hawaii and Wisconsin. But other states have balked at the idea, suggesting that the change could inconvenience voters and poll workers.

That hesitance reflects a move nationally away from the kind of overvote protections mandated for polling place voting machines by HAVA. The starkest example is the move to vote by mail. Twenty-seven states now have “no-fault” absentee voting, allowing voters to obtain an absentee ballot without an excuse. State elections in Oregon and Washington state are now entirely conducted by mail.

There are many reasons to adopt such policies, but we shouldn’t lose sight of their potential effect on the number of lost votes in future elections. When citizens don’t vote at their polling place, they receive no feedback or opportunity to correct their ballots if the machines can’t read their votes. And if states don’t make an extra effort to discern voter intent when machines can’t read votes, those votes will be lost.

Voters are much more likely to lose their vote when they cast their ballots by mail. In 2008, absentee voters in Florida were 54 percent more likely to overvote than voters who showed up at their polling place on Election Day. Researchers at the Massachusetts Institute of Technology and California Institute of Technology also found that the increased use of vote-by-mail in California — and the corresponding increase in the number of absentee overvotes — has all but counteracted the reduction in Election Day overvotes precipitated by recent improvements in voting-machine technology.

These fundamental changes in how people vote have made HAVA’s technological fix an even less potent defense against overvotes. So we must find other solutions to reduce the number of lost votes in 2012.

For starters, some states must fix their unnecessarily hard-to-read ballots. New York displays candidates for some contests across multiple rows of the ballot; this leads many voters, believing that each new row contains candidates in a different contest, to accidentally mark multiple candidates for the same contest. Fixing this ballot design problem is straightforward and would reduce the confusion that leads to overvoting in the first place.

We also need better data on the number of votes lost in polling places. Very few states keep public data on overvoting. Even fewer maintain precinct-level data. This information is needed to identify faulty voting machines and polling places that need better voter education and translation services. Legislators around the country should follow the Florida Legislature’s lead and require counties to report overvote data by precinct. Legislators should also mandate that state and local election administrators take all necessary steps to address election administration problems in high overvote areas.

The Help America Vote Act was an important opening salvo in the effort to prevent lost votes. But now is not the time to be complacent about that accomplishment. We must be cognizant of how recent voting changes might lead to lost votes, and we must take all feasible steps to ensure that every vote counts in 2012.

Sundeep Iyer is a fellow with the Brennan Center’s Democracy Program. Lawrence Norden is acting director of the Brennan Center’s Democracy Program.