The close and bitter Senate races around the country may be capturing the headlines, but buried in the fine print are some significant down-ballot effects on Tuesday in several states.

The Senate battle in Delaware is likely to hurt turnout by Republican voters, given the relative unpopularity of GOP nominee Christine O’Donnell — just a year before state lawmakers tackle redistricting after down-ballot state House races.

{mosads}The nastiness of the Illinois race between Rep. Mark Kirk (R-Ill.) and Alexi Giannoulias (D) could persuade voters to stay home in an election where several state offices are up for grabs, including attorney general, state treasurer and secretary of state.

And in Nevada, the lackluster appeal of both Sen. Harry Reid (D) and Sharron Angle (R) to some voters may also depress turnout in a year where the governor’s office is up for grabs.

Like most analysts, Jennifer Duffy, a senior editor at The Cook Political Report, sees a Republican wave down the ballot in most states regardless of circumstances. She’s done the math: Based on historical averages, Duffy says the average gubernatorial loss in midterm elections for the party with the presidency is 5.5. This year, though, it will likely be between 6 and 8. And while the average loss of state legislative seats is 217.5, Duffy says she has heard the Democrats’ losses could be about 500, more or less.

“We all know the party in power loses seats in a midterm election, right? That goes down the ballot,” she said. “Voters don’t discriminate. They look at the party affiliation and vote them out of office. And Republicans are just so fired up that I don’t think they’ll be turned off by the negative races.”

Perhaps most acutely, a down-ballot effect is likely in Delaware, where Democrat Chris Coons is leading O’Donnell. Because state GOP leaders had favored Republican nominee Mike Castle, a popular governor and congressman who had won 12 straight statewide races, some analysts see a low general-election turnout by GOP voters.

“No question about it, that will hurt Republicans down-ticket,” said Curtis Gans, director of the Center for the Study of the American Electorate at American University. “There are people who are Republican and don’t see Christine O’Donnell as a standard-bearer for the party.”

Tom Jensen, director of Public Policy Polling (PPP), which conducts a variety of national and state polls, also sees a negative down-ballot effect to O’Donnell.

“Ultimately Christine O’Donnell is going to be the face of the party’s slate, but having her as the nominee hurts with moderate voters and could have the potential to have independents simply vote Democratic,” Jensen said.

In Nevada, where Reid and Angle are virtually tied, Jensen and Gans said it is harder to predict the down-ballot effect of the two Senate candidates. The Silver State has a governor’s race this year, as well as contests for secretary of state, state treasurer and attorney general, plus a variety of referendum initiatives. One unique feature of the Nevada ballot: Voters can choose “None of the Above.”

The bitterness of the Nevada and Illinois contests could also depress turnout for one or both parties. Gans notes the successful 1998 campaign of Charles Schumer (D-N.Y.), who defeated former Sen. Al D’Amato (R-N.Y.).

“They had the most expensive, nastiest and closest race in New York history at the time, and they also had the lowest turnout race,” Gans said. “In the same year, there was an equally nasty race for governor in OH that set a new record low for turnout. There is lots of evidence that attack-ad campaigning will depress turnout. So a race can be close and mean without being mobilizing.”

Jensen sees exceptionally strong GOP Senate candidates like Kelly Ayotte in New Hampshire and Ron Johnson in Wisconsin with unique potential to help down-ballot Republicans in those states which have multiple House races.

But Jensen sees Illinois as Democrats’ biggest concern, and even the negativity of the Kirk-Giannoulias race isn’t likely to keep Republican voters home.

“We’re looking at a cataclysmic drop in turnout for Democrats there,” he said. “There’s an enthusiasm gap everywhere in the country, but it’s more pronounced in Illinois than anywhere else. They voted for ‘Hope and Change’ in 2008, and this election has nothing to do with ‘Hope and Change.’ That’s obviously affecting Democrats much more than Republicans. So there is big trouble down-ballot in Illinois.”

Duffy agreed.

“As nasty as that race has been, I don’t think Republican voters are going to stay home,” she said.