MADISON, Wis. — A record number of new voters are excited to vote for Barack Obama for president, but will they bother to support Democratic legislative candidates?

Some strategists say the answer to that question could help decide how well Democrats fare in statehouse races across the country.

With high turnout expected, both political parties and allied groups in states such as Wisconsin and Oregon are making a big push to reduce “voter dropoff” — the number of voters who cast ballots in the presidential race but leave the rest of their ballots blank. Democrats in particular are targeting the young voters who are crucial to Obama’s campaign but may have a greater tendency to ignore local races.

In the 2004 presidential election, nearly 7 percent of voters did not vote in U.S. Senate races and 13 percent didn’t vote in U.S. House races, according to a study by the U.S. Election Assistance Commission.

The commission did not study lower ballot races but drop-off can be as high as 20 percent in them, said Stephen Ansolabehere, a political scientist who has studied the phenomenon at Massachusetts Institute of Technology.

His study of 37,000 voters in the 2006 election found that less informed people have higher rates of drop-off but it’s not correlated to their age or race. States in which voters cannot vote straight-ticket by political party also have higher drop-off rates, he said.

He said the influx of millions of new voters this year may lead to a higher drop-off rate.

“Are they people who have gotten excited this year and learned a lot or are they people who normally don’t think about politics much and therefore have no idea who their state senator is?” Ansolabehere said. “If that’s the case, then they’ll drop off.”

Across the country, Democrats and allied groups say they are working to reduce that factor. In Oregon this month, the League of Conservation Voters sent its members an e-mail with candidates it has endorsed.

“Studies show many voters tend to be unfamiliar with down ballot races and they resist casting an uninformed vote,” the e-mail warned. “Here’s your chance to help your friends make informed choices.”

In Wisconsin, Democrats who are trying to control both houses of the Legislature and the governor’s office for the first time since 1986 say they are making it a top priority.

Some political scientists, including Charles Franklin at the University of Wisconsin, say young voters have the highest drop-off rates because they are less informed about local politics. Both parties and outside groups say they’ll appeal to these voters by emphasizing what’s at stake in legislative races and trying to send them targeted messages.

For instance, college students might receive phone calls or fliers from candidates promising to keep tuition affordable. A senior citizen? Prescription drugs.

“There will be a heckuva lot of effort to make sure these new voters don’t show up at the polls having never heard of their Senate candidates,” said Jason Childress, who leads the Senate Democrats’ campaign committee.

For instance, he said the party was targeting University of Wisconsin-Stout and UW-River Falls students to tout Page’s candidacy against Republican Sen. Sheila Harsdorf of River Falls. The seat is one Democrats are trying to pick up as they work to maintain control of the Senate, which they hold 17-15.

The state had one of the highest voter turnouts at 75 percent in 2004 but one of the largest drop-off rates in the nation. About 3 million voters cast ballots in the presidential race but 15 percent of them — or more than 415,000 voters — did not vote in Assembly races.

Republican Party executive director Mark Jefferson said the GOP is also targeting what he called “low-propensity voters.” He said they include young voters but also working-class voters and senior citizens who only routinely vote in presidential races.

“It’s not only getting them to the polls but getting them to care about the races beyond the presidential race,” he said. “We’re going to be focusing a lot of effort in that.”

In the GOP-controlled Assembly, he said some of the most competitive races include districts covering UW-Green Bay, UW-Whitewater, UW-Eau Claire and UW-Platteville, where Garthwaite is up for re-election.

Those districts are where this factor could have the greatest impact, Franklin said.

“In a close legislative race, that’s where young people can be swept up and vote a straight ticket and make more of a difference,” he said. “High student turnout plus low drop-off should help the Democrats in areas of high student concentration.”

Fair Wisconsin — a gay rights group credited with helping mobilize students to fight the gay marriage referendum in 2006 — is organizing on campuses and telling members that a Democratic Assembly would be friendlier to their interests, said executive director Glenn Carlson.

“There’s a huge drop-off and we’re trying to educate people about the importance of the Assembly and the differences in the candidates,” he said. “The biggest hazard with young people is to have them go to the polls and have them not know who the candidates for the Assembly are.”