(CNN) For two years Democrats have raged over Donald Trump's presidency, quarreled among themselves over the best strategy for responding to it, and above all, counted the days until next month's midterm election .

The biggest political questions facing Democrats, needless to say, all remain to be decided on election night. But that doesn't mean the tempestuous 2018 campaign season hasn't already sent important signals -- both encouraging and ominous -- about the Democrats' future against a Republican Party that Trump is reshaping in his image.

What follows is an attempt to identify some of the most important trends already evident on each side of that ledger for Democrats -- along with a few critical questions that remain very much to be decided.

The most encouraging trends for Democrats in 2018:

1. The white-collar suburban discontent with Trump is real and widespread.

The shift away from the GOP among white voters holding at least a four-year college degree is most intense among women, but also apparent among men. And those voters are retreating from the GOP not only along the East Coast (across Republican-held suburban seats in New Jersey, Pennsylvania and Northern Virginia) and the West Coast (in a concentration of five GOP-held seats around Los Angeles and another near Seattle) but importantly also through the center of the country. There, Democrats are poised to capture suburban seats outside Minneapolis, Kansas City, Denver, Detroit, Chicago and Tucson; have toss up chances in other seats near Des Moines, Salt Lake City, Detroit and Chicago; and have solid, though more challenging opportunities in Houston and Dallas. (More on that below.)

When the Washington Post/Schar School poll recently surveyed voters in 69 of the most competitive House districts they found that Democrats led among college-educated whites in them by fully 13 percentage points; by comparison, House Republicans carried those voters by nearly 20 point margins in both the 2010 and 2014 mid-terms, according to exit polls. Republicans respectively won control of the House and Senate in those midterms.

2. Democratic Senate and governor candidates in the Midwest are showing renewed competitiveness among blue-collar white voters who keyed Trump's victories in the states that propelled him into the White House.

Democratic Senate incumbents in Ohio, Wisconsin, Pennsylvania and Michigan -- all states won by Trump -- now appear solid favorites for re-election. The party is favored for the governorships in Michigan and Pennsylvania and locked in close races in Wisconsin, Ohio and Iowa -- the fifth Midwestern state key to Trump's 2016 victory. And it could pick up as many as four House seats combined in Iowa and Michigan.

In each case, that's at least partly because the Democratic nominees are posting much better numbers than Hillary Clinton among working-class white voters. Some of that may reflect what political professionals call "differential turnout" -- meaning that the non-college whites who dislike Trump are more likely to show up than the working-class whites who surged to the polls for him in 2016, but aren't as enthusiastic about conventional Republican candidates.

But Trump also appears to have suffered genuine erosion among working-class white women, largely because of his attempt to repeal the Affordable Care Act, and a sense among many that the improved national economy hasn't provided them appreciably more security. If that crack in Trump's armor persists to 2020, it would arguably provide the single most important advance for Democrats in the midterm election.

3. In a party whose national leadership is conspicuously older and whiter than its younger and multi-racial voting base, Democrats may transform their roster of elected officials with an array of diverse young leaders.

They have chosen the most women ever as nominees in House, Senate and gubernatorial races; picked a wide array of talented young national security veterans (a striking number of them female as well) in House contests; selected African-American gubernatorial nominees in three states, Latino nominees in three more, as well as a native-American in Idaho; and nominated several openly gay, bisexual or trangender candidates in high profile statewide offices (including Krysten Sinema in the Arizona Senate race and Jared Polis in the Colorado governor's contest.)

It's not hard to amass a list of Democratic House contenders who could graduate very quickly to future Senate nominations if they win next month: Mikie Sherrill in New Jersey, Conor Lamb in Pennsylvania, Jason Crow in Colorado, Dan McCready in North Carolina, Amy McGrath in Kentucky and Colin Allred in Texas among them. Alexandria Ocasio-Cortez will arrive in Congress from New York City an instant national figure among progressives. If Texas Senate challenger Beto O'Rourke wins or even recovers from his current polling dip to finish close to Republican Ted Cruz, he could quickly become a serious presidential contender.

Like the class of 1974 propelled into politics by the backlash against Richard Nixon and Watergate, the class of 2018 launched by the recoil from Trump could shape Democratic politics for years. "The 2018 [Democratic] class... will bring extraordinary number of national security experts into Congress at a time when America needs to reimagine its role in the world," says Simon Rosenberg, founder of the NDN, a Democratic advocacy and research group. "It is my bet that that the next 'John McCain' -- a proud passionate patriot --- will come from this class, and be a Democrat. "

4. The party has built a powerful national small-donor fund-raising base.

The vision of mass small contributor online fundraising earlier pursued in presidential races by Howard Dean, Barack Obama and Bernie Sanders has exploded from a niche opportunity to the default option for Democratic candidates this year. With the Democratic base's bottomless antipathy for Trump providing the fuel, mass donor fundraising is providing the party financial advantages that not long ago would have been unimaginable, especially when Democrats control none of Washington's power levers.

The poster child for this revolution is O'Rourke, who raised a head-spinning $38 million in just this year's third quarter. But more impressive may be the breadth of this financial river: the Democratic Congressional Campaign Committee says that in just that third quarter 30 Democratic House challengers raised at least $2 million, while another 30 raised at least $1 million. Those numbers are unprecedented and they suggest the Democratic presidential nominee in 2020 will have all the money he or she could possibly spend.

What's discouraging for Democrats in 2018:

1. Trump 's provocations alone show few signs of improving the subpar turnout patterns among Latinos and millennials, two core Democratic constituencies.

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In polls, both groups express preponderant opposition to Trump's posture on cultural and racial issues. But most polls suggest that their turnout next month will plummet compared to 2016, just as it typically has in midterm elections. Compounding the problem, when Latino turnout sags, what's left in the voter pool tends to be older and more Republican.

Democrats received encouraging news from Sunday's ABC/Washington Post poll, which found much higher levels of youth engagement than almost any other recent survey. But that result looks like an outlier compared to most other polls. And even if young people participate in somewhat higher numbers, their share of the vote could fall if they don't keep pace with the greater-than-usual midterm interest evident among other voter groups. By 2020, millennials will significantly exceed baby boomers as a share of eligible voters, but based on their turnout trajectory they will continue to lag them among actual voters. That would be a huge opportunity cost for Democrats given Trump's consistently low marks with the generation (apart from younger non-college whites).

2. White-collar suburbanites in the South still appear much more resistant to Democrats than elsewhere.

"The electorates there are definitely more conservative," says Democratic pollster Geoff Garin. "A Texas suburban voter is not the same thing as a New York suburban voter or a Denver suburban voter." A wide array of recent polls support that assessment. In Texas, O'Rourke has shown clear gains among college-educated white voters compared to earlier statewide Democratic candidates, but in recent surveys he's stalled out at around 40% of them, too little to win.

The New York Times/Siena College polls have found Democratic House candidates trailing among college-educated whites by about 20 points in two suburban North Carolina districts and by about 15 points in two suburban Texas districts. Stacey Abrams, the African-American Democratic gubernatorial nominee in Georgia, has also shown little progress with those voters.

The big exception is Andrew Gillum, the African-American gubernatorial nominee in Florida, who has run competitively with those voters in several surveys. But most of Florida more resembles the North in its cultural affinities; the larger trend is that ambivalence over Trump still doesn't appear to be moving a critical mass of Southern suburbanites, many of them culturally conservative Christians, away from the GOP.

3. Trump hasn't yet decisively tipped the Southwest toward the Democrats.

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As I've written before, Democrats over the long run will likely need deeper inroads in the Southwest to offset what's likely to be slow erosion in Great Plains and maybe also Midwestern states dominated by the older and blue-collar white voters that now consistently favor the GOP (even if Democrats trim those margins this year in the Midwest). Many Democrats hoped -- and Republicans feared -- that Trump could drive away Southwestern states through his anti-immigrant agenda and a suspicion of free trade that plays better in the industrial Midwest than in Western states with less manufacturing and greater ties to Mexico and other global markets.

But the key Southwestern states, while competitive, remain tough battles for Democrats. Democrats are favored in the governors' races in Colorado and New Mexico (more narrowly). But they are facing a dead-heat governor contest in Nevada and a likely landslide defeat against Texas GOP Gov. Greg Abbot. In Arizona and Nevada, Democrats are struggling in the Senate races much more than many in the party hoped, or even expected. Meanwhile the latest polls have shown Cruz comfortably ahead of O'Rourke, despite the Democrats' enormous crowds and fundraising. Apart from the Texas governor race, Democrats could still rescue any of these races. But their difficulty reflects the combined impact of the discouraging signs (1) and (2) just above: not enough Latino turnout (or margin) and insufficient inroads among white-collar suburban voters. Texas offers a variation on that equation tilted even more toward the GOP, largely because of point (4):

4. Outside of a few key Midwestern states, non-college whites in most places are still flocking to Trump and Republicans.

That tilt is most evident in the South: In the latest Quinnipiac University Texas Poll, Cruz was not only winning an incredible 86% of non-college white men but also almost three-fourths of blue-collar white women. In the New York Times/Siena surveys, the Republican nominees were winning about three-fifths or more of those voters in all four North Carolina and Texas suburban districts it has polled. Looking more broadly, the Washington Post/Schar poll found Republicans leading among non-college whites by double digits across the 69 battleground House districts it surveyed.

The bright spot for Democrats -- echoed in some, though not all, national polls -- was that the party faced only a single-digit deficit in that survey among non-college white women, less than it has typically confronted in recent House elections. Still the bulk of the evidence suggests that apart from a few admittedly pivotal-Midwestern states with stronger traditions of class consciousness and deeper union roots, Democrats still face a tough climb to recapture many working-class whites from the Trump-era GOP. That means the party will likely struggle next month to extend its House gains much beyond the white-collar suburban seats inside the major metropolitan areas where Trump is most toxic. And that means to the recapture the House majority, Democrats probably can't leave many of those top-tier suburban opportunities on the table.

What's still TBD for Democrats in 2018:

In one sense, the answer, of course, is that everything is still To Be Determined: the election results could scramble any of the conclusions offered above. But some questions seem especially uncertain and fraught with implications for the Democrats future.

1. Does mobilization tip Florida, Georgia or Texas?

Gillum, Abrams and O'Rourke are road testing the strategy that many liberals prefer for the presidential race: placing the greatest priority on expanding the electorate by turning out more minority and young voters rather than focusing on reassuring ordinarily Republican-leaning whites disillusioned with Trump. If any of those three win, it will be a great boost for 2020 Democratic candidates whose principal strength is their potential to mobilize younger and non-white voters. Kamala Harris, Cory Booker, O'Rourke himself, and -- in a slightly different way -- Elizabeth Warren or Bernie Sanders could benefit. More centrist white men including Joe Biden, Michael Bloomberg, Terry McAuliffe and John Hickenlooper could face tougher questions about whether they offer Democrats the best path to victory.

2. If Democrats take the House, can they use the platform to soften up Trump for 2020 or can he effectively use them as a foil?

The answer may turn at least partly on whether Democrats give him the contrast he's expecting, with a septuagenarian leadership headlined by Nancy Pelosi, 78. The alternative for Democrats is to make the same kind of generational change that Republicans did when they leapt from John Boehner (born in 1949) as speaker to Paul Ryan (born in 1970).

But Democrats won't need to confront that choice unless they can fill in a "yes" on the biggest question of all in 2018: will they win back the House?