Updated

As voters in 12 states headed to the polls Tuesday amid a growing anti-incumbent sentiment, voter turnout varied in states that will have the biggest impact in November.

In California, where former eBay chief executive Meg Whitman and former Hewlett-Packard CEO Carly Fiorina are GOP frontrunners for the governorship and Senate, respectively, turnout was expected to be relatively light -- with perhaps a third of registered voters casting ballots.

Of the 16.9 million Californians registered, 40 percent -- or 6.8 million -- requested vote-by-mail ballots. As of Monday, 1.8 million of those ballots had been returned.

In Arkansas, however, voters streamed to the polls to decide whether incumbent Sen. Blanche Lincoln should keep her seat. The "Blue Dog" Democrat is competing in a heated runoff against Arkansas Lt. Gov. Bill Halter, who has the backing of labor unions and liberal groups.

Primary voting appeared on pace in Nevada for an expected turnout of about 25 percent in Las Vegas, the biggest city in a state where Republicans are picking a nominee to challenge Senate Majority Leader Harry Reid.

Republicans are also deciding whether to nominate troubled Gov. Jim Gibbons for a second term or choose former federal judge Brian Sandoval to oppose Democrat Rory Reid, the Senate Majority leader's son.

Political observers predicted that a high voter turnout in the state would benefit state Assemblywoman Sharon Angle, a tea party favorite who has enjoyed a surge in the polls in recent weeks. Angle is competing against but businessman Danny Tarkanian and casino executive Sue Lowden.

Election officials have been predicting turnout at 25 percent statewide.

Clark County elections chief Larry Lomax described voter turnout as a "mixed bag" in the state, the Las Vegas Sun reported. Lomax said certain polling places, like in Sun City, had a higher than usual turnout while others reported low numbers, according to the newspaper.

In South Carolina, turnout was expected to run ahead of 2006 levels. Voters there will voters will whittle a field of seven candidates for governor and set up the race for a U.S. Senate seat during primary elections that also will be pivotal for three congressional elections.

Fox News' Carl Cameron and the Associated Press contributed to this report