Lake County, the state's second-most populous with nearly 500,000 people, had reported no results as of 11 p.m. EDT. A large number of absentee ballots and a record turnout delayed the tallies, and polls there close an hour later than much of the state because Lake is in the Central time zone.

In the rest of the state, Clinton was leading 52 percent to 48 percent.

Lake County, which runs along the southern shore of Lake Michigan, is an amalgamation of steel mills and chemical plants in cities with large minority populations such as Gary and Hammond, along with numerous mostly white suburbs to the south. It always has had more in common with neighboring Chicago than the rest of Indiana. As such, it was expected to favor Sen. Barack Obama in the Democratic presidential race.

The county is in the Chicago television market, where the Illinois senator has received plenty of coverage since being elected in 2004.

Another factor is race. Lake County is the state's most diverse, with 26 percent of its population black and 14 percent Hispanic.

The county has long been a Democratic stronghold and a key to the party's hopes in statewide races. In 2004, it provided nearly 12 percent of all the votes John Kerry received in Indiana.

Clinton and her husband made numerous campaign trips to Lake County, hoping to gain advantage among its Hispanic and blue-collar white voters.