In short, there's a lot to pay attention to — and the results should yield plenty to unpack one year from Election Day 2016.
Here are the top eight political dramas Tuesday and what you should watch for in each of them:
1. Kentucky: Can Democrats hold off a troubled GOP outsider?
In some ways, Kentucky's gubernatorial election is a microcosm of what's happening on the national level. A self-funded, sometimes politically awkward outsider is drawing the attention of the media and the wary embrace of the GOP establishment.
Republican Matt Bevin, a millionaire investor, is cruising around Kentucky in a gold Cadillac Escalade with a Donald Trump-like message that he's the man for the job because he can't be bought. Bevin squeaked by GOP veterans like Agriculture Commissioner James Comer in a nasty, soap opera-like primary this spring. The rest of Bevin's campaign has hardly gone smoothly either. Read this column.
He's now narrowly trailing Democratic Attorney General Jack Conway for the open seat in a state where political power is divided but Republicans were hopeful of a pickup. As the AP notes, Democrats control statewide offices and the state House, while the GOP controls the state Senate and the congressional delegation. Also in the mix is independent Drew Curtis, who could tip a tight race one way or the other.
One of the top issues: Obamacare. Popular outgoing Kentucky Gov. Steve Beshear (D) expanded Medicaid for more than half a million people in the state as part of President Obama's 2010 health-care reform law, and the election is becoming a referendum on whether that was the right move.
(Note: The other big governor's race of 2015 -- in Louisiana -- already held its open primary Oct. 24. The runoff is not Tuesday, but rather on Nov. 21.)
2. Virginia: A super-tight state Senate battle
All 140 state legislative seats are up for reelection in Virginia on Tuesday, but just a handful could change the balance of power in this swing state.
Specifically, we're talking about the very evenly split state Senate, which Gov. Terry McAuliffe (D) has said must swing Democratic so he can try to expand Medicaid (sensing a theme here?) and pass gun-control legislation.
Republicans have an overwhelming majority in the House, but in the Senate they hold a slight edge of 21 seats to Democrats' 19. In other words, Democrats have to hold on to every one of their seats — which is not a given — and pick up another just to reach a tie, write The Washington Post's Laura Vozzella and Rachel Weiner.
Republicans are struggling with holding onto seats amid changing demographics. Whether to increase tolls in a commuter-heavy Northern Virginia district up for grabs has shaped up to be the issue that could decide the Senate's fate.
3. Mississippi: Can people sue for their education dollars?
The governor's race is a bust for political junkies. Republican incumbent Gov. Phil Bryant is expected to run away with it after little-known truck driver Robert Gray, whose own mother apparently didn't realize he was in the race, won the Democratic nomination.
But of note is a citizen-sponsored constitutional amendment that, according to the AP, would allow residents to sue the state to get more money for schools.
It essentially pits supporters of the amendment, who feel lawmakers have shortchanged public schools by not fully funding them according to a 1997 law requiring just that, against some of their lawmakers. Republican leaders in the state legislature argue this amendment would give judges too much control over state funding and have introduced a counter ballot initiative.
4. Ohio: Changing the pot legalization game?
On Tuesday, Ohio could become the first Midwestern state and fifth state overall to legalize recreational marijuana. But what's even more notable is what would happen after pot is legalized: Cultivating and selling pot would be limited to 10 pre-determined farms in the state. Any pot distributor in Ohio would have no choice but to buy marijuana grown from one of these farms. It would make about two dozen investors, including pop star Nick Lachey, very rich.
A diverse group of opponents that includes some marijuana legalization advocates are arguing this particular method of legalizing — a constitutional amendment by ballot initiative financed almost exclusively by those who stand to gain from it — undermines the social justice and civil liberty goals of legalizing marijuana in the first place.
The initiative is so controversial that state lawmakers introduced their own ballot initiative. Known as the "anti-monopoly amendment," it would prevent anyone from enshrining something in the state constitution for financial gain.
Voters appear split on what to do. And if both amendments pass, we could be in for a court battle.
5. Colorado: What to do with that marijuana cash
Legalizing marijuana is old news for Colorado, which along with Washington state became the first to do so in 2012. And now it's making enough money that on Tuesday voters will decide what to do with the $66 million in extra tax revenue from its sales (more tax revenue than the state made in alcohol during the same time period).
State law requires excess tax influx to be given back to taxpayers. That averages to about $8 a taxpayer. A ballot initiative is asking voters to let the state keep the excess tax revenue and spend it on school construction, marijuana education courses and youth-mentoring services. (A significant portion of tax revenue from pot sales in Colorado already goes to needy schools.)
The Denver Post editorial board has encouraged voters to vote yes, saying, "In a nutshell, the money kept by the state would be directed at doing a lot of good."
But there's a robust argument against the proposition, including the argument that instead of returning the money to taxpayers, the state should sock it away to pay for expanding government services that will eventually be required to regulate this ever-expanding industry.
6. Houston: A hotly contested LGBT rights law
In addition to the six-way open mayoral race in the nation's fourth-largest city, voters will decide whether to uphold a 2014 law that prohibits discrimination on the job and in housing, including for sexual orientation.
As Texas Monthly columnist Mimi Swartz notes, Houston is the only major U.S. city without such a law. This is despite the city being the largest in the country with a gay mayor. Outgoing Mayor Annise Parker (D), got it passed in 2014, but opponents challenged it in court, and the courts sent the law back to Houston voters to decide what to do.
Among a group of social conservative opponents, the law is being cast as the "bathroom ordinance" or "bathroom bill" because it would allow transgender women (those who are born men but identify as women) to use the women's bathroom. "Any man at any time could use the women's bathroom," argues one ad.
One poll reported by Texas Monthly shows support for the Houston Equal Rights Ordinance, or HERO, at a toss-up. Voting is predicted to be anemic; Swartz says in 2009, for Parker's election, 19 percent of the city showed up to the polls.
7. Salt Lake City: A gay mayor in Utah?
The mayoral race for Salt Lake City has shaped up into a two-way fight between incumbent Ralph Becker (D), who's running for a third term, and former state lawmaker Jackie Biskupski (D).
Biskupski appears to have the edge; the single mother has the endorsement of the Salt Lake Tribune. What's interesting about the race is that Biskupski would be only the second woman to run Salt Lake City and the city's first openly gay mayor.
On the surface, Biskupski's election would seem unusual for a town that is the capital city of a Republican state and headquarters of the Mormon church, which spent more than $20 million campaigning against legalizing same-sex marriage in California last decade.
But there are signs social norms are changing; in January, the Mormon church announced it is now campaigning to support anti-discrimination laws aimed at protecting LGBT Americans. And as far back as 2005, Salt Lake City was named in an LGBT-oriented travel book among the 51 most gay-friendly places to live in America.
8. Pennsylvania Supreme Court: A very important court
Three out of the seven spots in Pennsylvania's state Supreme Court are up for grabs on Tuesday, which could mean one of the biggest court shake-ups in recent history.
There's a lot at stake after Election Day, too. From Phillymag.com's excellent voter guide (there's also a mayoral race in Philadelphia):
The high court could well end up making the ultimate call on an array of highly charged ideological matters in the next few years, from gun control, to legislation limiting abortion access, to school funding, to the drawing of legislative districts.
That includes whether Pennsylvania, a swing state, leans Republican or Democratic in the decades to come, settling lawsuits between more gun-control focused Philadelphia and the pro-gun rest of the state, deciding Voter ID initiatives, and hopefully departing from the court's scandal-plagued past (recent justices have resigned in e-mail porn scandals and amid corruption charges).