A U.S. Senate seat in Indiana is up for grabs after Sen. Dan Coats announced earlier this year that he is retiring. The race will likely be one of Indiana's most contentious races in 2016, and there is no clear frontrunner.
Who ultimately gets the seat will depend on a multitude of factors. Here are five that we know will play a role:
1. Who's Running and What They Stand For
The Republicans have three candidates:
Former State GOP Chair Eric Holcomb, Sen. Dan Coats' former chief of staff
Rep. Marlin Stutzman, R-Indiana 3rd District
Rep. Todd Young, R-Indiana 9th District
The three candidates all have significant political experience, but they play to different constituents.
Holcomb, who also worked for former Gov. Mitch Daniels, is what many consider the establishment candidate. He's run multiple political organizations and knows the political system well.
Congressman Stutzman, on the other hand, is the Tea Party favorite.
"He's essentially an insider who plays the role of an outsider," says political analyst Ed Feigenbaum. "He's a guy who's not worried about stepping on toes. He's not worried about offending the establishment. He's made it clear he's willing to take on his own party's leadership."
Congressman Young is the GOP's "policy" candidate. His years working on complex issues in Congress, at times with Democrats, could give him an edge over his opponents if he can play on his experience.
"He's a really bright guy who understands the intricacies of things like tax policies," Feigenbaum says.
Former Congressman Baron Hill, D-Indiana 9th District, is the only announced candidate for the Democrats. Hill aims to set himself up as the candidate for the working class. He's well liked among Democrats, but he is by no means a "fresh face," which could be a disadvantage.
He previously served as a representative from 1999 to 2005 and then again from 2007 to 2011 when he was defeated by Todd Young.
2. More Candidates Expected
The filing deadline to enter the U.S. Senate race isn't until February 2016 for major parties. That means there is still plenty of time for other candidates to get into the race.
State Sen. Mike Delph, R-Carmel, spent the last four weeks in Washington D.C., raising suspicions that he might enter the race. Delph's ultra-conservative views mean he could pull votes away from Congressman Stutzman.
Former Governor and Senator Evan Bayh has been long suspected of another Senate bid, especially after announcing earlier this year he would not run for governor, but analyst Ed Feigenbaum doesn't think that is likely.
Rep. Christina Hale, D-Indianapolis, was considering a run, but decided against it.
3. The National Picture
Democrats need four seats to take back the Senate, and Indiana could be a point of focus for the party.
Analysts at the national blog FiveThirtyEight say Sen. Dan Coats' retirement means there is a chance Democrats could pick up the seat.
Indiana isn't Utah. Donnelly was close in the polls to Mourdock even before Mourdock's infamous remarks. And Democrats came close to winning the other major statewide race that year, the gubernatorial contest. Not to mention, President Obama carried Indiana in 2008.
The point is that a Senate race in Indiana is winnable for Democrats - especially in a presidential year, without fear of the midterm penalty.
Analyst Ed Feigenbaum says whether Democrats have a chance depends heavily on the GOP primary.
If a far-right candidate like Congressman Stutzman, who appeals to the Republican base but not necessarily to a more moderate majority, gets the nomination, Democrats have a better chance of winning.
Indiana's other senator, Joe Donnelly, is also a Democrat.
That could either have primed the pump for another Democratic senator or created worse odds for liberals in the state. The last time Indiana had two Democratic senators was from 1963–77 when Van Hartke and Birch Bayh, Evan Bayh's father, held the seats.
4. Other Races' Influence
As mentioned, the fact that it's a presidential year could impact the race, although it's too soon to tell how.
Having Hillary Clinton, as opposed to Bernie Sanders, on the presidential ticket, could also bring out voters in northwest Indiana, which might tip the scales for Democrats.
A contentious gubernatorial race could also have some sway.
"If it looks like the Democrats stand a really good chance in the governor's race, then you'll see national money coming in for both the governor's race and the U.S. Senate race because the Democrats want to keep the top of the ticket together," Feigenbaum says.
5. The Geographic Advantage
Name recognition is key in any election, and the U.S. Senate race is no exception.
Rep. Todd Young likely has the biggest advantage here.
He's well known (if not well liked) in Bloomington, his wife is from Paoli and he grew up in Carmel, providing him what Feigenbaum calls "essentially three hometowns."
Young's district also spans a wide swath of the state, including the northern part of Louisville and the southern part of Indianapolis.
"He's in two of the district's largest media markets," Feigenbaum says. "People are familiar with seeing him on TV, and that's a big factor in building that ID and comfort zone."
Then again, Eric Holcomb has the backing of Sen. Coats, which provides him a good statewide base.
Rep. Stutzman, while not especially known across the state is very well known in his district, which has helped him raise small-dollar donations - something Feigenbaum says shouldn't be discounted.
