When Florida's votes were counted on Election Day, Gov. George W. Bush of Texas had a tiny but possibly decisive edge: the majority of the state's black voters, Vice President Al Gore's most reliable voters, stalwart supporters, cast their ballots on punch cards that are more prone to voter error and miscounts.  Across the state, nearly 4 percent of the type of punch-card ballots most widely used in Florida were thrown out because the machines read them as blank or invalid. By contrast, the more modern, optical scanning systems rejected far fewer votes -- only about 1.4 percent of those cast.

A New York Times analysis shows that 64 percent of the state's black voters live in counties that used the punch cards while 56 percent of whites did so. While black voters made up 16 percent of the vote on Election Day, that small difference, the analysis suggests, could have had a decisive effect on an election decided by only a few hundred votes out of nearly six million. Exit polls show that blacks voted overwhelmingly for Mr. Gore.  Vice President Al Gore raised the issue of the disproportionate effect of the punch-card ballot yesterday as he defended the Democrats' demands for recounts in three counties that used them. "The old and cheap, outdated machinery is usually found in areas with populations that are of lower income, minorities, seniors on fixed incomes," Mr. Gore said.

In Florida, county officials determined in each county what kinds of machines to use for voting. In some of the counties where punch cards are used, the officials are Republicans; in others, they are Democrats.  While Mr. Gore was citing the differences in voting systems as part of his argument for a recount, Allan J. Lichtman, chairman of the Department of History at American University in Washington, who has testified in dozens of voting rights lawsuits, said they could violate federal law, even if the variations were not intentional or politically motivated.

"If minorities have less of an opportunity to participate fully in the process, that's a direct violation of the Voting Rights Act," Mr. Lichtman said.

When optical ballot scanners are used, voters mark their choice with a pencil next to the name of their candidate. This appears to make them less susceptible to voter error.  The large number of ballots in Broward, Palm Beach and Miami- Dade counties in which the paper punch-card machines detected no choice for president has stirred controversy.  Democrats say many of these ballots were failed attempts to cast votes; Republicans say these voters had no preference for either candidate or failed to register their choice correctly.

A survey of several large Florida counties turned up an anomaly: Floridians whose ballots were read by the machines as not registering a choice for president were much more likely to have voted with computer punch cards.

In Orange County, the largest to use the optical equipment, only 1 in 300 ballots was blank in the presidential race. In Manatee and Brevard Counties, the rate approached 1 in 800. Mr. Bush easily carried Manatee and Brevard Counties while Mr. Gore prevailed in Orange.

The punch-card-voting counties, by contrast, had sharply higher numbers of people tallied as having no vote for president. In Miami-Dade, the Florida county with the most votes cast, the machines read 1 in 60 ballots as having no vote for president. In Hillsborough, near Tampa, it was 1 in 67. And in Pinellas County, it was 1 of 96.

Mr. Gore won Miami-Dade and Pinellas while Mr. Bush carried Hillsborough.

The Times analysis showed that registered Democrats in Florida were only slightly more likely to vote in counties that use punch-card machines than Republicans. But 63 percent of Mr. Gore's votes were counted on the type of punch-card machines at issue in Palm Beach County, compared with 55 percent of Mr. Bush's.  Statewide, the pattern was reversed on the optical scan systems. Forty percent of the Bush votes were tallied on these systems, compared with 33 percent for Mr. Gore.  (continued)