Happy primary day, Hoosiers! Indiana is easily forgotten on the primary calendar, sandwiched as it is between sexier states like Pennsylvania and Maryland (don't look at me like that — have you seen that flag?). But if you care about how well Congress functions, you'll want to pay attention to today's primaries, even if you don't watch "Stranger Things" and "Parks and Rec" on repeat.

As my colleagues recently so beautifully illustrated, there are several parties within the parties in Congress. On the Republican side, there are pragmatists who fall in line with party leadership — and then there are obstructionists who tend to make life harder for them.

This year, there are three open House seats in Indiana that could send either type of representative to Congress. And because these seats are safely Republican, today's contests, not November's, will effectively determine that. Elsewhere in the state, Rep. Victoria Spartz — the Hamlet from Hamilton County — could be the second incumbent representative of the cycle to lose reelection, and GOP primary voters will also choose who will likely become the next chief executive of this state of nearly 7 million people. So yeah, the stakes are high!

We won't have to wait long to find out the winners: Polls close in most of Indiana (the parts in the Eastern time zone) at 6 p.m. Eastern, with the parts of the state in the Central time zone following suit at 7 p.m. Eastern. Follow along with us for the next few hours, won't you?

—Nathaniel Rakich, 538

Another ex-congressman may make a comeback in southwestern Indiana's 8th District — once one of the most competitive seats in the country but now a reliably Republican seat. The two front-runners in the GOP primary here appear to be state Sen. Mark Messmer and former Rep. John Hostettler. Establishment and tea party Republican groups have invested heavily in this race: America Leads Action has spent $1.6 million to help Messmer and hurt Hostettler, and Protect Freedom PAC is airing ads for Hostettler.

But the main divide in this race seems to be less about governing philosophy and more about foreign policy. For instance, Protect Freedom PAC — which represents former Rep. Ron Paul's libertarian wing of the party — may be with Hostettler because he and Paul were two of only six Republicans who opposed the Iraq war back in 2002. And Hostettler's record on Israel has provoked strong opposition from the American Israel Public Affairs Committee and Republican Jewish Coalition. Citing anti-Israel votes Hostettler took in Congress as well as a book he wrote that blamed the Iraq war on Jewish Americans' efforts to help Israel, these two groups have dropped $2.2 million to attack Hostettler or boost Messmer.

In total, pro-Messmer, anti-Hostettler outside groups have outspent pro-Hostettler, anti-Messmer groups by a whopping $5.1 million to $793,000. (And it's not like Hostettler himself has been able to fight back; Messmer has outraised him $763,000 to $41,000.)

Don't write off two other candidates, either. Surgeon Richard Moss, who has pledged to join the Freedom Caucus, has raised $556,000, while 28-year-old Army reservist Dominick Kavanaugh took in $528,000. That said, given the financial disparity, any candidate other than Messmer has to be considered an underdog.

—Nathaniel Rakich, 538