Just over half of all active Nevada voters have already cast their ballots in early and absentee voting, but it's the half that has yet to vote that will make all the difference in two closely-watched Nevada congressional contests.

In the 2nd and 3rd districts, the campaigns for Democrats Jill Derby and Dina Titus both said they are happy with early voting figures showing Democrats participating at higher rates than Republicans. In Clark County, where Titus is running against third-term U.S. Rep. Jon Porter (R-Henderson), Democrats are trouncing Republicans 51 percent to 32 percent, according to early voting statistics. In Washoe County, where Derby is trying to oust freshman U.S. Rep. Dean Heller (R-Carson City), early-voting Democrats were outnumbering Republicans 45 percent to 38 percent.

An exit poll of early voters conducted by the Las Vegas-based DNA Communications Consulting Group on Oct. 28 showed Derby leading Heller 55 percent to 44 percent.

It's those voters who haven't cast their ballot yet that are keeping aides to Derby and Titus up at night.

"I think it's a great sign," Titus spokesman Andrew Stoddard said of the early voting figures, then adding: "We're going to work as hard as we can to get voters who haven't voted to vote."

Titus and Derby are locked in competitive races with their opponents. Newly-released polls conducted for the Las Vegas Review-Journal show Titus and Porter tied at 44 percent and Derby trailing Heller 50 percent to 37 percent.

Even after the early voting turnout, analysts say Democrats will need to drive substantial support to the polls on Tuesday to offset heavier Republican turnout that day. The chief concern for Democrats is that those seen as lower propensity voters whom they are counting on to carry them over the top, especially the Hispanic community, won't show up. Hispanics account for 15 percent of the population in both districts.

Both campaigns have been targeting Hispanic voters heavily in the final hours before polls open. Titus's campaign has released a flood of Spanish-language mail, while Derby has is airing ads in Spanish on radio stations and in newspapers. Derby also spent Monday campaigning with U.S. Rep. Loretta Sanchez (D-Calif.).

Erik Herzik, a University of Nevada at Reno political scientist, said Democrats had to be worried about getting the remaining voters out to the polls.

For Democrats, Herzik said, "In the back of my mind is the worry that, ‘Will people show up?' They haven't in the past, particularly in Clark County."

But, Herzik said that with Democrats energized like never before that probably won't be a problem this year.

Democrats privately hold out hope that Republican voters in the state are less energized than usual and may be less likely to show up to the polls than in years past.

But Republican operatives insist that isn't the case, and argue that GOP voters in the rural areas of Heller's district are especially reliable.

"We'll see a lot more Republicans on Election Day," predicted Ryan Erwin, a Nevada-based Republican consultant.

In Porter's case, simply turning out Republican voters won't be enough. Democrats now outnumber Republicans in the district by 35,000. Porter's campaign says it has been aggressively courting independent and potential crossover voters, and believes its TV ad campaign has successfully raised doubts about Titus among voters across the board. The National Republican Congressional Committee and the conservative advocacy organization Freedom's Watch have also pitched in with ads hitting Titus as a tax-raiser.

"Jon Porter has proven his resiliency by battling back into a neck-and-neck contest. He is used to having to put together a coalition of Republicans, Democrats, and Independents, and we are confident that he can do it again," said Ken Spain, an NRCC spokesman.

In the 2nd district, Spain argued that even with the early voting surge Derby wouldn't be able to make up the GOP registration edge.

With pre-election polls showing Barack Obama leading John McCain in the Silver State, analysts say the Democrats' success could hinge on whether enthusiasm for Obama transfers to down ballot races. Erwin, the GOP consultant, said he had seen exit polling in Henderson showing between 10 percent and 12 percent of Democrats leaving the booth after voting for Obama.

But Democrats reject that assertion. "People are looking for change across the board," said Kristen Cullen, a Derby spokeswoman.

If Republicans have less difficulty getting their voters out to the polls, they face another challenge: overcoming the deficits they face after early voting in the state.

"The question is, how big a deficit are they going to have to overcome?" said David Damore, a University of Nevada at Las Vegas political scientist. Damore estimated that Republicans would need to beat Democrats by seven to 10 percent on Election Day.  

For now, Democrats say they couldn't be happier with the early voting figures.

"Nevada families want change," Yoni Cohen, a Democratic Congressional Campaign Committee spokesman, wrote in an e-mail message. "Jill Derby is running strong in early voting because Nevadans realize they just can't afford Dean Heller."