An examination of 175,010 Florida ballots that were not counted in the 2000 presidential election provided further evidence that the ballots of voters in the state's black neighborhoods were most likely to go uncounted last November.

One reason black voters had more uncounted ballots, according to the study by The Washington Post and other media organizations, was that ballots in predominantly black neighborhoods were twice as likely to have no indication of any vote for president. In heavily black areas, 13 of every 1,000 ballots had no mark, compared to 6 in 1,000 in white neighborhoods.

Another reason was the disproportionate number of "overvotes" -- instances where more than one mark was made on a ballot.

Black precincts had a heavy concentration of overvotes that were rejected by counting machines on election day. White precincts using the same technology -- Votomatic punch cards -- had a different pattern of errors: They had a higher rate of incomplete punches such as dimples or "hanging chads."

In The Post's study, voter intent on many overvotes could not be determined. But in many instances voter intent could be established from examining the chads, providing a big boost for Republican George W. Bush from predominantly white voters. In Duval County, which had the highest rate of uncounted ballots in the state, Bush picked up 989 votes in The Post study.

Overall, 136 out of every 1,000 ballots in heavily black precincts were set aside -- a rate of spoiled ballots that was three times higher than in predominantly white precincts. Those precincts, where at least 80 percent of the voters were white, had 45 out of 1,000 ballots disqualified.

The difference in spoiled ballots between white and black voters was greatest in some counties that use paper ballots marked with a pencil and are read by optical scanning machines. In those "optical-scan" counties that transport ballots to the county seat to be tallied, black voters were almost four times as likely as whites to have cast ballots where no votes were counted.

The rate of spoiled votes was much lower in the state's 26 optical scan counties, where the ballots are tallied at the polling places, and voters who make an error in filling out the ballot are alerted and allowed to revote. Because of this "second chance" technology, black voters were just under two times as likely as whites to have ballots tossed out. The technology reduced the difference in spoilage rates by more than half.

"Clearly there are radical differences between the two systems," said David Bositis, an authority on the black vote at the Joint Center for Political and Economic Studies, a think tank focusing on minorities' electoral participation.

"Given that 9 of 10 black voters were voting Democratic, and two-thirds of white voters were voting Republican, this [reliance on voting machinery lacking the second chance option] represented a net advantage for the Republicans" in the thousands of votes, Bositis said. "That's not minor."

The ballot study suggested that black voters stand the most to gain from election reforms in Florida and other states that require polling places to install "second chance" technology.

Florida Gov. Jeb Bush (R) and the Republican-controlled legislature have mandated that counties install voting systems with the technology. Several other states -- such as California, Maryland and Georgia -- are doing the same, election experts said.

"Because of what we learned in 2000, almost every new election system purchased everywhere from here on out will have second chance technology," said R. Doug Lewis,executive director of the Election Center, a nonpartisan group that advises and trains election officials. "We've been trying to say to African-American and inexperienced voters that we, too, are concerned about any system that allows voters to be disqualified."

Second chance technology is designed to prevent overvotes, the most common form of invalid ballot. Al Gore was listed in 80,772 of the overvotes examined in the ballot study, twice as many as George W. Bush.

Thousands of Florida voters using optical-scan technology created overvotes by marking the oval next to a candidate, then filling the oval next to "write-in" and writing the same candidate's name, called a "double-bubble."

The Post ballot review found that Gore could have had a net gain of 662 votes in a hand recount of optical overvotes, almost entirely because of those double-bubbles.

But the statewide recount ordered by the Florida Supreme Court, and stopped by the U.S. Supreme Court the following day, specified only undervotes would be examined and not overvotes. Part of the federal court's reason for ruling the recount unfair was that it would give undervotes a chance to be fixed but not overvotes.

Democrats and African American leaders have charged repeatedly that black voters were disproportionately affected by the state's election procedures, including confusing ballot designs and instructions. The U.S. Commission on Civil Rights issued a report in June criticizing management of the Florida election for disenfranchising voters, particularly blacks.

The report, approved in a 6 to 2 vote that split along party lines with Republican-appointed members dissenting, said that problems with voter registration and improper attempts to remove felons from the rolls were compounded by inadequate voting equipment and voter training.

Gore campaign strategist Ron Klain says ballot reviews show "the larger number intended to vote for Al Gore."