Welcome to 2020 Vision, the Yahoo News column covering the presidential race with one key takeaway every weekday and a wrap-up each weekend. Reminder: There are 111 days until the Iowa caucuses and 385 days until the 2020 election.

With the clock ticking down toward the start of voting, Democratic candidates are getting more serious - and desperate. Twelve among those still running qualified to appear Tuesday night at Otterbein University in Westerville, Ohio, hosted by CNN and the New York Times - the largest field ever to assemble on one stage for a presidential debate. All of them have the same basic checklist of avoiding gaffes, scoring a viral moment and remembering to plug their website, but each also has a specific agenda, based on their poll standing and positioning. Here is what each hopes to achieve tonight:

THE FRONTRUNNERS

Status update: Warren is literally the only major candidate who is doing better in the polls now than she was at the start of the summer, having clawed her way back from single digits to lead Joe Biden in Iowa, New Hampshire and many national surveys. Lately she's been picking a fight with Facebook over its policy of allowing politicians to lie in ads; to make her point, she posted an ad on the network with the intentionally false claim that Facebook CEO Mark Zuckerberg had endorsed President Trump for reelection.

Tonight's goal: Warren has enjoyed a long run of good press and kid-glove treatment from her rivals. In recent weeks, several of them - Pete Buttigieg, Bernie Sanders, Biden - have signaled that the honeymoon is over, launching mild attacks (from both sides) on Warren over her position on Medicare for All. But nothing has knocked the Massachusetts senator off her stride. They'll almost certainly try again tonight, giving Warren a chance to show off her defensive skills - and, if she succeeds, to continue to build momentum.

Status update: For weeks now, the former vice president has been fending off an onslaught from the current president over Ukraine, with Trump trying to falsely tar Biden and his son Hunter, and Biden struggling to respond. But it's important to note that Biden's poll numbers haven't declined at all over that period (even as Warren's have risen). And lately he seems to have found his footing, unveiling an ethics plan on Monday that directly targets Trump and accuses him of creating the "most corrupt administration in modern history."

Tonight's goal: A plurality of Americans now say they believe Trump's accusations are hurting Biden's prospects of becoming the Democratic nominee. Biden's job Tuesday night is to prove them wrong - to show on live national TV that he can handle the incoming. His main rivals might be wary of attacking him about Ukraine, lest they appear to be endorsing Trump's attack, but the moderators are almost sure to ask about it - especially since Hunter Biden just gave his first interview on the subject to "Good Morning America" Tuesday morning.

THE SLEEPER

Status update: Buttigieg was the fundraising leader in the second quarter of 2019, and he raised nearly $20 million in Q3. Other than Warren, he has built the biggest and best early-state ground game. He has the cash and campaign infrastructure to go the distance. But after peaking in the spring, Buttigieg has failed to take off in the polls - with one exception: Iowa. There, the South Bend, Ind., mayor has gained 5 points over the last month, in large part by positioning himself as a center-left alternative to Warren and Biden.

Tonight's goal: It's all about Iowa. Buttigieg is banking on a surprisingly strong showing in the Hawkeye State - and perhaps a Biden stumble - to propel him into later contests. As such, he has been advertising against Medicare for All Democrats such as Warren and Bernie Sanders and seeking to prove his moderate bona fides by attacking Beto O'Rourke over gun buybacks ("a shiny object") and O'Rourke's intention to strip anti-LGBTQ churches of their tax-exempt status. Expect more of the same Tuesday night.

THE COMEBACK KIDS

Status update: Earlier this month, Sanders suffered a heart attack that forced him to briefly halt campaigning. In the interim, he has continued to release plans to hike corporate taxes, to rid politics of corporate money and to empower workers. But Sanders's path to the nomination was already narrow before he was hospitalized, and his poll numbers seem to have declined another 2 percentage points amid fears that his health and age might make it harder for him to compete with Trump.

Tonight's goal: His campaign hopes the debate will mark Sanders's triumphant return to the trail. Voters will be watching the Vermont senator for any sign of fragility or lack of stamina. A sure-footed performance will go a long way toward reassuring voters. But it may not be enough to actually increase his support in the polls, which is what he needs to do to win.

Status update: Harris entered the Democratic primary to acclaim, but she has failed to transform compelling moments - including her takedown of Biden during the first round of debates - into a coherent message, and she has suffered in the polls, slipping from a high of 15 percent in July to the mid-single digits. Her recent focus on "prosecuting the case against Trump" hasn't moved the needle.

Tonight's goal: Create another big moment - probably by bashing Trump - then somehow make it stick. Like Buttigieg, Harris is going all-in on Iowa; unlike Buttigieg, she's been unable to gain much traction there. Another star turn on the national stage could win her a second look. But time is running out, and it's getting harder and harder to see how Harris can mount a comeback with a strategy that hasn't worked for her in the past.

THE CANDIDATES WHO ARE MOSTLY RUNNING FOR VEEP AT THIS POINT

Status update: Like Harris, O'Rourke launched his campaign amid sky-high expectations - and as with Harris, his actual campaign has fallen short. Even a much-publicized reset after the August mass shooting in El Paso, Texas - a shift that has seen O'Rourke throw political caution to the wind on guns, gay rights and other hot-button issues - has failed to change his polling numbers, which have been stuck in the 2 percent range since July.

Tonight's goal: As the two youngish white guys in the race, Buttigieg and O'Rourke have been using each other as convenient punching bags for weeks now - Buttigieg to show off his centrism, O'Rourke to criticize said centrism. Expect that dynamic to continue tonight. But at this point O'Rourke, who retired from Congress earlier this year, probably isn't playing to win so much as positioning himself for whatever comes next.

Status update: It's worth noting that with her brand of no-nonsense, Midwestern pragmatism, the Minnesota senator is doing better in Iowa than anywhere else. But when "better" means sixth place, you know your campaign is in trouble. Klobuchar - like O'Rourke, Julián Castro and Tulsi Gabbard - hasn't even qualified for the November debate yet.

Tonight's goal: Continue questioning the party's leftward shift and arguing that she can win in the Rust Belt. But with Biden in the race there doesn't seem to be room for another moderate, so Klobuchar's message will probably be targeted more at the candidates who could eventually pick her as a running mate than anyone else.

Status update: At the end of the last fundraising quarter, Booker threatened to end his campaign unless his supporters kicked in $1.7 million over 10 days. They came through, and the New Jersey senator posted his best quarterly report to date ($6 million). But with Biden dominant among black voters, and Harris better positioned to capitalize if the former VP slips, it's unclear how Booker expects to win the nomination.

Tonight's goal: Booker has consistently turned in some of the best-received debate performances, and despite his sunny message, he hasn't been afraid to "draw contrasts" with other candidates - including Biden and Buttigieg, whom he has accused of " doing the NRA's work for them." Don't be surprised if Booker does the same again tonight - and if voters still don't seem to care.

THE CANDIDATE WHO'S TOTALLY RUNNING FOR VEEP AT THIS POINT

Status update: A standout performance in the first round of debates - Castro pummeled his fellow Texan O'Rourke - has kept the former HUD secretary alive. But a thinly veiled swipe at Biden's age and memory during the last debate damaged his net favorability rating by 10 percentage points, and his reputation hasn't recovered.

Tonight's goal: With no discernible path to the nomination, Castro's best hope now is to re-endear himself to both rank-and-file Democrats (so he can qualify for the November debate) and his fellow candidates (so, as the only Latino in the race, he can stay near the top of the list of possible running mates). In other words, don't expect any new kamikaze missions.

THE SIDESHOW

Status update: A tech entrepreneur making his first run for office, Yang has gotten farther than anyone expected on the strength of his common-sense rhetoric, extensive, unorthodox policy proposals - including his signature universal-basic-income plan - and his "Yang Gang" online fanbase. But "farther than anyone expected" has still left him lingering around 2 percent in the polls, and there's pretty much zero chance the party will nominate him.

Tonight's goal: Speak up. At September's debate, Yang spoke for about eight minutes, total - 90 seconds less than the next quietest candidate (O'Rourke) and roughly half as much as his top-tier rivals. Yang has the cash to keep campaigning, and he's already qualified for November's debate. But to transform his 2020 bid into something else - a UBI think tank? a book deal? a big tech gig? - he needs to stay in the limelight.

THE TROUBLEMAKERS

Status update: This billionaire San Francisco hedge funder and longtime climate change activist is making his debate stage debut after spending millions in early states and on Facebook ads to qualify. He's pledged to spend $100 million of his own money on the campaign - more than any of his Democratic rivals has raised to date. And with 8 million people on his email list - names gathered during his pre-Ukraine impeachment push - Steyer has by far the largest address book in the field.

Tonight's goal: Introduce himself - and force everyone else to acknowledge his existence. Most voters have no idea who Steyer is, so expect him to push his almost Trumpian message ( I'm a political outsider who can't be bought) by taking swipes at more traditional Democrats, and to sound brash notes on both climate change and impeachment in an attempt to get noticed.

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Status update: A longtime source of controversy in Democratic circles for her anti-interventionist, anti-establishment views, Gabbard failed to qualify for the last debate and noisily threatened to boycott this one, arguing that Democratic Party leaders "are trying to hijack the entire election process." But on Monday she backed down.

Tonight's goal: Throw bombs. In her last debate, Gabbard went hard at Kamala Harris, ripping her record as a prosecutor. She trended online as a result. Expect her to reprise that strategy Tuesday night, perhaps by targeting other candidates or the Democratic Party itself. And thanks to her controversial views on Syria, where the pullout of American forces has led to a humanitarian disaster, Gabbard will probably get more speaking time than her low poll numbers might otherwise merit.

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