WASHINGTON — Democrats are finally ready to begin voting on their nominee for president this week after a year of campaign pitches from dozens of candidates. Along the way, the campaigns have put out an ambitious slate of plans that have driven a fierce debate about what it means to be a Democrat in 2020, with everyone from a self-described socialist in Sen. Bernie Sanders, I-Vt., to one of the richest men in the world, former New York City Mayor Michael Bloomberg, contributing to the pile.

Depending on how they choose, the party could take a fundamentally direction on health care, taxes, trade, or education.

Here are some of the biggest splits that have emerged between the candidates when it comes to their platforms.

"Medicare for All" — or for all who want it?

By far the largest and most consistent policy fight has been on health care, which voters also rate as their top concern in issue surveys. The main driver of this debate is Sanders’ Medicare for All proposal, which would effectively eliminate every existing private plan and replace them with a government program that covers health, vision, and dental care with no premiums or deductibles.

Sanders and his allies have argued it's the best way to make sure every American is covered, to eliminate needless overhead, to force down surging drug and hospital prices, and to give a boost to workers whose paychecks have been increasingly eaten up by premiums and out-of-pocket costs.

Opponents point to its high cost — one independent estimate pegged it at $34 trillion in additional federal spending over ten years — and disruption, especially its elimination of competing private insurance. They've proposed a range of alternatives, some closer to the current system and some closer to Medicare For All, that are centered on offering a subsidized public insurance option alongside private plans.

Candidates have found themselves at times uncomfortably trying to straddle the divide between the two approaches. Sen. Kamala Harris, D-Calif., co-sponsored the Sanders plan in the Senate and endorsed it on the trail, only to grow uneasy with some of its features and retreat to a still-sweeping proposal with a larger role for private insurance. Sen. Cory Booker, D-N.J., another co-sponsor of the Sanders bill, decided to run on a public option in 2020.

Former Texas Rep. Beto O’Rourke walked back his prior support for the Sanders approach and backed a House bill that, while more far-reaching than plans like former Vice President Joe Biden's or former South Bend Mayor Pete Buttigieg's, would preserve some private insurance options.

Sen. Elizabeth Warren, D-Mass., initially avoided committing to one approach or another, only to back the Sanders plan in the first debate and then tweak it with her own proposals to finance it and to pass it in two parts, with private insurance only being eliminated in the second bill. But while health care has long been a rallying cry for Sanders with his supporters, Warren dropped in the polls as attention shifted toward her plan, with some Democrats fretting about its political viability.

How left is too left?

The Democratic party has moved left overall since 2016, even as the primary still features a raging debate between moderates, progressives, and socialists about its overall platform. On once-contentious issues like federal funding for abortion, LGBT rights, and marijuana, for example, the presidential field has largely settled on a consensus.

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But the lack of conflict on various issues has also created incentives for candidates to embrace new or once-obscure ideas in order to distinguish themselves from the pack and drive discussion of their top issue priorities. In each case, they forced the field to quickly decide if these proposals were workable and whether they genuinely reflected the party’s base or were just a passing hashtag on Twitter.

On immigration, former HUD Secretary Julian Castro proposed making border crossings a civil offense rather than a criminal offense. Criminal prosecutions, once rare, have surged in recent decades and culminated in the Trump administration's “zero tolerance” policy that prompted the child separation crisis, which Castro argued his changes would prevent. Warren and Sanders sided with Castro while others, like Biden, argued it was an unnecessary fix to a problem that could be solved from the White House instead.

On guns, Beto O’Rourke and Rep. Eric Swalwell broke from the party’s usual calls for increased background checks and reinstating an assault weapons ban and demanded that gun owners also give up assault weapons they currently own, under penalty of law. “Hell yes, we're going to take your AR-15,” O’Rourke said in a September debate. None of the remaining frontrunners bit on the idea.

And on criminal justice reform, Sanders went beyond typical Democratic calls to restore voting rights for felons and suggested allowing prisoners to vote while still serving their sentence. None of his rivals embraced the idea, though some have said they were open to considering it down the line.

Free for all — or free for some?

Many of the debates between the Warren and Sanders wing and their more moderate rivals have centered on whether new government benefits should apply equally to all Americans or only to the middle class and poor.

The central front in this fight has been higher education, where Warren and Sanders favor tuition-free public college while Biden, Buttigieg, and Klobuchar favor more targeted benefits that exclude students from higher-income families.

“I very much agree with Senator Warren on raising more tax revenue from millionaires and billionaires," Buttigieg said in a December debate. "I just don't agree on the part about spending it on millionaires and billionaires when it comes to their college tuition."

Warren also wants to use $640 billion raised from her proposed wealth tax to cancel up to $50,000 in student debt for households making under $250,000 a year while Sanders would go further and wipe out all $1.6 trillion in student debt, period.

“I happen to believe that when you talk about programs like Social Security, like healthcare, like higher education, they should be universal,” Sanders told MSNBC’s Chris Hayes in December.

A similar debate has played out over entrepreneur Andrew Yang’s call for universal basic income, which would provide everyone with a $1,000 payment per month regardless of income or wealth.

What is the "Green New Deal?"

The presidential campaign has taken place in the shadow of the Green New Deal movement, which has focused activist energy on climate change and led Democrats in Congress to draft a resolution outlining an ambitious transition away from fossil fuel.

But the Green New Deal resolution is only a call to action, not a detailed policy proposal, which has left it to the candidates to decide what it means in practice.

Washington Governor Jay Inslee took a lead role early on, pitching himself as the sole candidate who would focus on climate above all other issues.

While his campaign didn’t take off, many of his ideas did, and the candidates ended up adopting broadly similar plans to invest trillions in clean energy research and infrastructure, to encourage rapid adoption of electric vehicles and to tighten regulations on pollution.

They weren’t identical, though, and several found ways to push the policy debate into new territory. Sanders proposes $16 trillion in new spending, several times more than anyone else’s climate plan. Billionaire philanthropist Tom Steyer has promised to use emergency powers to advance his climate agenda. Sanders and Warren also propose banning fracking, a technique used to extract natural gas, which goes too far for Biden and others in the field. Yang has distinguished himself with a call for research into “geo-engineering” technology that could artificially cool the Earth in order to buy more time to fix the problem.

Changing the system

Hardened by years of fruitless struggles to move nominees and legislation, several Democratic candidates have argued for changes to make it harder for the minority party to stymie legislation. Some have also pitched ideas to potentially defang a conservative-leaning Supreme Court or to bypass Congress to pursue more of their agenda through executive action. ­

Warren and Buttigieg have called for an end to the legislative filibuster. Buttigieg drew attention early on for his call to expand the Supreme Court to fifteen seats and divide it equally between five Democratic and five Republican-approved judges and five consensus choices backed by the other nominees themselves. Much of the field called for ending the Electoral College and moving to a national vote for president, an idea with new momentum among Democrats after Trump lost the popular vote by 2.8 million votes just 16 years after President George W. Bush won the White House despite trailing Al Gore by over 500,000 votes nationwide.

But others worry about upending longstanding institutions, especially candidates who have spent significant time working in them, and have raised concerns that the other side would retaliate with similar changes. Senator Michael Bennet repeatedly slammed his head on a table when the Washington Post asked him about expanding the judiciary. Biden and Sanders have both expressed unease with the concept as well as ending the filibuster (although Sanders proposed a potential way to bypass it). Biden is also opposed moving to a national popular vote.