New Orleans voters have a big decision on their hands this fall, when they'll choose Mayor Mitch Landrieu's successor.

They've also got a big decision in the special election to replace former treasurer and now U.S. Sen. John Kennedy — which, while statewide, could well be decided in the city.

One reason is that, across Louisiana, New Orleans has the only really major races on the ballot, what with an open election for mayor and several competitive City Council contests. There are a few big-ticket elections elsewhere, including a Public Service Commission contest in Acadiana, but nothing will rival an open mayor's race for interest.

That's means that turnout will likely be higher there than in other parts of the state, giving the city's vote proportionately more weight.

The other reason has to do with party.

New Orleans voters lean heavily Democratic. In 2016, 81 percent of the Orleans Parish vote went to Hillary Clinton, and in 2015, 87 percent of voters chose John Bel Edwards over David Vitter for governor. If a well-known Democrat were part of the treasurer field, there's no question that person would dominate the New Orleans vote.

But there are no prominent Democrats in the race, and that presents a couple of scenarios.

One is that many voters will either skip the race or go with the only Democrat on the ballot, Harvey attorney Derrick Edwards, who has never held public office and has so far not reported raising any money. Even should New Orleans give Edwards enough support to make the runoff versus one of the better-known Republicans, he'd be an underdog in a state that leans heavily to the right.

The second option is the more interesting one. With no major candidate of their own, Democratic voters can become the swing bloc that might deliver victory to the Republican they like best.

One candidate for the office, state Sen. Neil Riser, of Columbia, learned about this dynamic firsthand. Riser ran for Congress in the conservative 4th District in 2013, and wound up in a runoff against a less ideological upstart named Vance McAllister, a fellow Republican who appealed to Democratic voters by questioning the GOP party line against expanding Medicaid under the Affordable Care Act. In the end, those Democrats carried him across the finish line.

Riser would likely have a hard time appealing to New Orleans voters, and may focus his efforts more on consolidating support in north Louisiana.

Another conservative, former lawmaker John Schroder, of Covington, could make a play as the regional candidate. But while he's got a populist streak, Schroder's voting record may not impress Orleans voters. One issue that will surely come up is his refusal to push for the recommendations of a task force on taxing and spending during the recent legislative session, even though he authored the measure to create it in the first place, because he claimed it focused too much on raising revenue.

Better positioned was a lawmaker who will not appear on the ballot, state Rep. Julie Stokes, of Kenner. Before pulling out of the race following a breast cancer diagnosis, Stokes had been making the rounds in New Orleans, and both her proximity and her record in the Legislature could have given her an edge. Stokes broke from the staunchly anti-tax bloc of House conservatives and proved willing to work with Edwards to address the state's perennial fiscal crisis. That's the sort of thing that would have gone over well in New Orleans, where the governor remains popular.

The wild card is Angele Davis, a Republican and former top aide to both the Democrat Landrieu, when he was lieutenant governor, and Republicans governors Mike Foster and Bobby Jindal. Davis, of Baton Rouge, isn't well-known in the city, but if she positions herself as a moderate and reaches out successfully, she could develop a following.

The challenge for any of these Republicans is how to appeal to Democratic voters, particularly in New Orleans but also across the state, without alienating Republicans in the process.

That's how it sometimes goes in a state where elections don't automatically come down to D-versus-R showdowns. Louisiana's nonpartisan voting system can definitely make things unpredictable. It also makes them interesting.

Follow Stephanie Grace on Twitter, @stephgracela.