The fate of mayoral and City-County Council candidates in Tuesday’s election is likely to come down to turnout in a few key districts, including Center Township and southern Marion County.

Political science experts say each party’s get-out-the-vote efforts will be critical this year, particularly for council races that have drawn little voter interest.

“It’s basically who turns out their base,” said Brian Vargus, a political science professor at IUPUI who studies voting patterns. “The Democrats have a bigger base, but will they vote?”

Democrats indeed have the demographic advantage; the party led Republicans in straight-party voting in Marion County by 20,975 votes in the 2010 election.

But that didn’t bring them victory in 2007, when Republican Mayor Greg Ballard defeated incumbent Democrat Bart Peterson and Republicans took control of the council, due in part to lower-than-usual turnout in traditionally strong Democratic areas.

This time around, targeting large swaths of voters in Center and Warren townships will be particularly important for Democrats, Vargus said, as will drawing high turnout among African-Americans, who make up a major part of the Democratic base.

For Republicans, the southern Franklin, Perry and Decatur townships will be key.

Ed Treacy, chairman of the Marion County Democratic Party, said his party’s strategy since 2004 has been to target every Democratic voter in every precinct, including those that have as few as one Democrat. That was a shift in strategy from earlier years, when Democrats focused on the areas where their base was strongest.

 “Once we started working every precinct, we starting winning the elections,” Treacy said.

Republicans, meanwhile, have been making a strategic push to conduct “the largest get-out-the-vote effort in possibly the history of Marion County Republicans,” said Kyle Walker, the party’s chairman. That has included phone calls, door-to-door efforts and community meetings.

And while Republicans lag demographically, Walker said there’s a strong base of independent voters in the county, as evidenced by the 2008 election, when Republican Gov. Mitch Daniels and Democratic President Barack Obama both won the county by strong margins — 48,357 and 105,816 votes, respectively.

Drawing independents is a viable strategy, Walker said, “particularly in a municipal election when the issues that will be governed by the ultimate winners are very close and very important to voters.”

“Municipal elections are very candidate-driven,” he said.

It’s unclear how many independent voters reside in Marion County, but Vargus agreed that a large swath of independents could tip the balance for either Ballard or Democratic challenger Melina Kennedy. Still, he thinks party-based voting will drive turnout in this election, as it does on the national level.

So far, early voting, including in-person, absentee and overseas ballots, has been stronger this year than in 2007, when there were 10,267 early ballots cast with three days remaining until the election. As of Sunday, this year's tally was 18,055.

But Vargus said that’s not necessarily an indication of strong turnout on Tuesday. He anticipates turnout will be lighter than in 2007, when it was about 27 percent.