In Clark and Washoe counties, Democrats have been voting at higher rates than Republicans since early voting began Oct. 18. However, Republicans have narrowed the margin somewhat.

On the first day of early voting, 62 percent of Clark County voters were Democrats, while 23 percent were Republicans and the rest nonpartisans or members of minor parties. Through Sunday, 55 percent of early voters were Democrats, 29 percent Republicans.

Of all registered voters in Clark County, 47 percent are Democrats and 32 percent are Republicans.

In Washoe County, 51 percent of the early voters through Sunday were Democrats, while 33 percent were Republicans.

Exit polling of early voters conducted by a local political consultant suggests a close presidential contest in the Silver State: Democratic nominee Barack Obama had the votes of 50 percent who had voted, while Republican nominee John McCain had 48 percent of the early vote.

The poll, conducted by Las Vegas-based consultant Steve Nathan's firm Dialing Nationwide Automatically, or DNA, was conducted by automatically dialing everyone who had voted through Friday, based on statewide voter records, and weighting responses to reflect the composition of the electorate so far.

Nathan said the statewide numbers were based on 7,147 responses to the survey. He said McCain was getting much of his support from rural and Northern Nevada.

Experts caution that it is important to take such data with a grain of salt because it reflects only who has voted, not who intends to vote.

"There's no way to know what the turnout will be on Election Day," said Larry Sabato, director of the Institute for Politics at the University of Virginia. "Every vote counts the same. One that's cast at one minute to 7 on Nov. 4 carries exactly the same weight as one that was cast by absentee ballot a month ago."

Exit polling data, he said, provides valuable information about who has voted and how, but it should not be used to forecast how the election will turn out.

Sabato, whose "Crystal Ball" tracks his election predictions, foresees Nevada going narrowly for Obama. He also predicts that Rep. Jon Porter, an incumbent Republican, will not survive his challenge from state Sen. Dina Titus, D-Las Vegas.

The DNA exit poll surveyed that race, the 3rd Congressional District, and found Titus leading in the early voting. She had 51 percent of the vote while Porter had 46 percent through Friday, based on 3,095 responses.

Nathan, who earlier this year ran unsuccessfully in a Democratic state Senate primary, said his firm conducted early-vote exit polling for several local races in 2006 with "extremely accurate" results.

Early voting continues through Friday. Hours and locations vary. Registered voters should check the sample ballot they received in the mail for details, or check online at www.accessclarkcounty.com/depts/election.