Midterms are theoretically local and state elections, but Tuesday's contests add up to a remarkable snapshot of a quickly changing America: more women running than ever ... more Muslim Americans ... more Native Americans ... more veterans ... more teachers ... more millennials ... and more LGBTQ Americans.

• With turnout expected to hit record levels, the results will tell us a lot about the type of candidate who matches up best against Trump in 2020.

Here are 6 things I'm watching:

1. Will either party find a way to arrest what The Wall Street Journal calls "The Yawning Divide"? White women with college degrees are turning rapidly Democratic, and white men are moving drastically the other way, "making both essentially unreachable by the opposing candidate."
2. Will pollsters make a comeback after being stunned in 2016? The WashPost's Philip Bump reminds us that based on polling science, "If we held the election 20 times, in three of those elections, the Republicans would hold their [House] majority. Next Tuesday might be one of those three."
3. Will young people vote more than in the past, after all the pleas, from the Parkland survivors to "Pod Save America"? The #MarchForOurLives and #RoadToChange activists traveled the country to try to counteract apathy among vote-eligible teens. It'd be a game-changer if they do, but Democratic strategists have their doubts.
4. How big a swath of that record number of women candidates for House, Senate and governor — spurred by record number of women donors — turn into lawmakers? Many are challengers — always a daunting route. Christina Reynolds of EMILY's List told AP: "[R]egardless of what happens, women have shown that they are no longer happy with other people representing them and speaking for them."
5. How blue is the wave? Republicans are favored to pick up several Dem open seats in western Pennsylvania and the Iron Range of Minnesota. But will a single Democratic House incumbent lose? Probably not. The Cook Political Report's David Wasserman tells me the nation's most vulnerable House Dem is Rep. Tom O´Halleran in Arizona. But he's still favored to hold his Trump-won seat.
6. And from Jonathan Swan: If Democrats win control over the House by a slim margin (e.g., 5 to 10 seats), how tight will Nancy Pelosi’s grip be on power? There’ll be a ton of pressure for generational change, and much restlessness beyond those candidates who’ve already publicly said they won’t vote for Pelosi as Speaker. On her side: Pelosi is the perfect person to keep a rowdy House on track to investigate the heck out of the Trump administration. 

Be smart ... On Wednesday morning, we'll wake up with the next two to six years foretold:

• Trump: triumphant or cornered?
• Democrats: ascendant or humiliated?

Either way, we face a 2020 political season that will make this one seem civil.

It's unanimous! The latest race ratings from the Cook Political Report, Sabato's Crystal Ball from the University of Virginia's Center for Politics, and FiveThirtyEight all show Dems on the cusp of winning the House, with Rs likely to hold the Senate (and even pick up a seat or two).

We selected the Axios 8 to include not just high-profile races, but ones that would only be competitive if the "blue wave" is massive.

The bottom line: Democrats are still riding a "blue wave" — but it's not strong enough to help them win all the races that looked within their reach earlier in the cycle.

The Axios 8 for 2018:

1. Texas Senate: A recent Quinnipiac poll showed Sen. Ted Cruz with a five-point lead over Democrat Beto O'Rourke. Texas turning blue would be a sign of an impressive "blue wave." As a symbol of the heightened interest, more than 3.6 million people have already voted early in the race, vs fewer than 2.1 million in 2014.
2. Ohio governor: Both Trump and Mike Pence are making last minute stops in Ohio where Democrat Richard Cordray is leading Republican Mike DeWine by an average of 4.7 percentage points; but compare that to the Senate race, where Democratic Sen. Sherrod Brown is leading Jim Renacci by 16 points. A Cordray win could mean Democrats have a shot at other Midwest governorships.
3. West Virginia's 3rd district: The latest poll shows Republican Carol Miller leading Democrat Richard Ojeda by five percentage points, and Trump is visiting the area four days before the election. If Democrats win here, it validates the party's strategy of targeting over 100 GOP-held districts.
4. California's 45th district: If Democrat Katie Porter defeats Rep. Mimi Walters in this previously solid-Republican, Orange County district, they're likely to do well across southern California and are in good shape to take the House.
5. Minnesota's 8th district: This was always the most vulnerable seat for Democrats, but the latest NYT/Siena College poll has Republican Pete Stauber leading by 15 points. It could be a rare House gain for the GOP.
6. Texas' 23rd district: Republican Rep. Will Hurd has had to distance himself from Trump, but it looks like he's out of danger in this swing district. Voters now prefer him over Democrat Gina Ortiz Jones by 15 percentage points.
7. Florida's 26th district: Republican Rep. Carlos Curbelo is trying to keep his seat in a district won by Hillary Clinton. In September, he was leading Democrat Debbie Mucarsel-Powell 47% to 44%, but now she's leading 45% to 44%.
8. Iowa's 3rd district: Cindy Axne, with the backing of high-profile Democrats like Barack Obama and Sens. Kamala Harris and Amy Klobuchar, is leading Republican David Young in NYT/Siena College polls. If this seat flips, some Democratic strategists think that bodes well for flipping Iowa's 1st district, too.

Go deeper: The Axios 8: How to tell the strength of the "blue wave"

By the time it's over, the 2018 midterms will have smashed the previous midterm spending record, with candidates spending a combined $5.2 billion, according to a projection by the Center for Responsive Politics. The previous record for midterm spending was about $4.2 billion in 2010, adjusted for inflation.

The biggest donors (latest data via OpenSecrets.org):

1. Sheldon and Miriam Adelson ($113 million, all to Republicans and allies)
2. Thomas and Kathryn Steyer ($51 million, all to Democrats and allies)
3. Richard and Elizabeth Uihlein ($40 million, all to Republicans and allies)
4. Michael Bloomberg ($38 million, almost all to Democrats and allies)
5. Donald Sussman ($23 million, almost all to Democrats and allies)

The most expensive races (by amount spent from OpenSecrets.org):

1. Texas Senate, $94 million
2. Florida Senate, $91 million
3. Georgia House district 6 special election, $46 million
4. Missouri Senate, $42 million
5. New Jersey Senate, $38 million

Go deeper: Explore the graphic on the most expensive races.

The 2018 midterms could have the largest gender gap since 1958. Just look at these numbers from the cycle so far:

• Women prefer Democrats by a 16-point margin (58% to 42%) and Republicans win men by a 17-point margin (50% to 33%), per a new Quinnipiac University poll.
• More women than men have voted early in key battleground states like Georgia (56%); Texas, Florida, and Tennessee (all 54%); Nevada (53%) and Montana (52%).
• 42% of all Democratic nominees for House, Senate, and governor are women, compared to just 14% of Republican nominees. For Congress overall, Democrats have nominated 198 women to Republicans' 59.
• In midterms since 2006, more women than men have voted by margins between 4 and 10 points. In the 2016 election, 10 million more women were registered to vote than men.

The bottom line: "The level of enthusiasm among women is going to bear directly on Democratic success," said Jennifer Lawless, a politics professor at the University of Virginia. "If there is a 'blue wave,' that will exist in part because of women."

A new poll from Harvard Kennedy School's Institute of Politics found 40% of millennials (18- to 29-year-olds) are likely to vote in the midterm elections on Nov. 6.

Why it matters: Millennials overwhelmingly lean Democrat, and many Democrats are hoping young voters will help build their "blue wave" on election night. The Harvard poll found among those millennials likely to vote, they prefer Democrats to control Congress by a 34-point margin (66% to 32%).

By the numbers: Midterm turnout among voters under 30 has only exceeded 20% in two elections since 1986, when it reached 21% that year and again in 1994.

• Interest in voting among millennials has increased by three percentage points since Harvard's poll last spring.
• While interest among millennials of both parties has increased since then, the share of Republican millennials who are likely to vote shot up by 7 percentage points since the spring, compared to a three-point spike for Dems.
• President Trump's approval rating is 25% among likely millennial voters — 17 percentage points lower than his national average.

One more thing: A majority of millennials support the Democratic socialist agenda — 56% support a federal jobs guarantee with a $15 minimum wage; 56% support free tuition at public and community colleges; and 55% support Medicare for All.

Go deeper: At least 600 millennials are running for office in 2018.

A slim majority of the midterm congressional campaign contributions from America's biggest companies have gone to Republican candidates, an analysis of federal election data by Axios' Harry Stevens shows.

• There's been a "notable shift toward the Democrats" in the period right before the general election, according to Sheila Krumholz of the Center for Responsive Politics. (There was no such shift in the 2014 midterm election, and in 2010 the shift was toward the Republicans, she said.)

Why it matters: America's wealthy companies are able to influence elections by financially supporting candidates whose positions align with their values — or who they believe can help their businesses. But even more often, they support both sides, ensuring access to whomever ends up in power.

Go deeper: The interactive graphic

Some of the most memorable and creative ads of the 2018 cycle:

• "Helmer Zone" is hilarious. Dan Helmer may have lost his primary to challenge GOP Rep. Barbara Comstock, but this ad (bad karaoke in a bar!) lives on. Watch.
• "Women Rising" by Serve America PAC shows a montage of the many women vets who are running for office for the first time this cycle. It's the Year of the Woman with a little Bruce Springsteen and a lot of patriotism. Watch.
• "They're doing fine, are you?" is one of the funniest ads this cycle. It's just a bunch of senior citizens saying things like "Dear young people, don't vote!" and “Climate change? That’s your problem. I’ll be dead soon." Watch.
• "Casey," the ad from Florida's GOP gubernatorial nominee Ron DeSantis, is one of the more memorably pro-Trump ads of the cycle. He's teaching his kid to build a wall with blocks! Watch.
• "This Will Save Lives," shows Levi Tilleman, who lost his House primary in Colorado, willingly getting pepper sprayed in this gun control ad. Watch.
• "Dead Wrong," from Sen. Joe Manchin has him shooting the lawsuit that could kill Affordable Care Act protections for people with pre-existing conditions. Watch. (And remember his 2010 ad, "Dead Aim," when he shot a cap-and-trade bill. Watch.)

Midterm elections have historically been a no-lose scenario for stocks. Dating back to the 1950s, the S&P 500 has always been higher a year after the midterms, no matter the outcome, writes Axios' Courtenay Brown. According to Capital Ideas, stocks in the year following midterms have performed twice as well as other years.

Bottom line: Markets may shrug if there is a Democratic sweep, because the next Congress is "very unlikely to undo the major market-impactful legislation that has already been passed under President Trump," like tax cuts, strategists at UBS point out.

• If Republicans maintain control, stocks could jump higher temporarily, Art Hogan, a strategist at investment firm B. Riley FBR said, because investors will think "here comes more deregulation, and tax cuts 2.0 — but then they will realize we might have more work to do than that."

The impact on the economy is more uncertain.

• If Democrats take the House and the Senate, brace for "slower economic and employment growth," since it eliminates the possibility of another tax-cut boost to the economy, John Herrmann, who heads up interest rate research at MUFG Securities, wrote in a note.
• Gridlock won't "capsize the economic boat," S&P Global's chief economist Beth Ann Bovino wrote in a research note, but it will create big questions around government spending, which boosts economic growth.

What to watch: The midterms are in "second place" on investor's minds after worries about China and trade, Hogan said.

• Bonus data point: The S&P 500 had its worst October in a midterm year since the 1970s, per data compiled by lobbyist Bruce Mehlman.