(CNN) Go big or go home might be the new motto for the Democrats' sprawling cast of 2020 presidential contenders.

At a moment when the country remains closely divided between the two major political parties, the 2020 Democrats are rushing to propose expansive and expensive proposals that envision massive change in public policy across a wide array of issues.

The scale and sweep of these ideas -- on issues from health care, climate change and college affordability to voting rights and tax policy -- represent one of the defining choices for the party heading into the 2020 contest with President Donald Trump.

Given the tumultuous nature of Trump's presidency, Democrats could have concluded that the way to victory in 2020 is to promise voters a "return to normalcy" and a lessening of political conflict. Instead, even the most centrist contenders -- including front-runner Joe Biden -- are betting that Trump's norm-shattering presidency has demonstrated that voters are receptive to big change, even if that means pitched political battles in Washington.

"The truth of it is Trump has shown ... that there's a strong appetite for bold solutions to significant problems," says Neera Tanden, president of the Center for American Progress, a leading liberal think tank. "Trump's disruption, and many of his lunatic ideas, have widened the aperture of what's acceptable in the policy debates."

At various points earlier in the race, candidates have proposed a massive federal investment in raising teacher salaries, mandatory federal approval of state abortion laws, allowing felons to vote while still incarcerated, ending the Electoral College, big tax cuts for middle- and lower-middle-income families, forgiving virtually all student debt, federally funded "baby bonds" targeted especially at low-income children, establishing universal pre-K and tuition-free public college, creating a statutory federal right to abortion, legalizing 11 million undocumented immigrants, renewing the ban on assault weapons and, of course, replacing private health insurance with a government-funded single-payer health care system. Even the more centrist alternative on health care -- allowing all Americans to buy into Medicare -- would constitute a huge expansion in government's involvement in the medical system.

The eventual nominee isn't likely to endorse all of these ideas. But that list testifies to the rise in Democratic ambitions -- and expectations. Cumulatively, the 2020 agenda rivals or even exceeds the magnitude of President Lyndon Johnson's Great Society during the 1960s. It far exceeds the legislative ambitions of Barack Obama and Bill Clinton, the last two Democratic presidents.

In many ways, the scale of the 2020 Democratic proposals reflects a consensus across ideological lines in the party about one reason for Hillary Clinton's defeat in 2016. Though Clinton also offered a wide array of plans to address many issues, hardly any were large or compelling enough to capture the public's imagination.

That led many Democratic strategists to conclude that she failed to provide voters a pithy answer to what is sometimes called the Ted Kennedy question: Why are you running for president? ( Kennedy memorably flunked that question with a stumbling answer in an interview with CBS' Roger Mudd when he announced his primary challenge to President Jimmy Carter in 1980.)

This time, Democrats have almost universally concluded that big ideas signal to voters a big commitment to improve their lives.

"Incremental solutions communicate that the problem is not so large," Tanden says. "That is what Trump championed. If you think the problem is big you have a bold solution to it. I think that makes sense to people."

Large plans -- and huge plans

Significant differences in scale remain within the Democratic field. Warren, with her "I've got a plan for that" mantra, has set the pace for comprehensive proposals; Sen. Bernie Sanders of Vermont, while he has added relatively fewer new plans this time, isn't far behind her with the big agenda he identified in 2016, led by a single-payer health care system and free tuition at public colleges and universities.

At the other end, Biden and several candidates trailing in the polls -- Sens. Amy Klobuchar of Minnesota and Michael Bennet of Colorado, as well as former Colorado Gov. John Hickenlooper -- have generally offered more restrained promises. Yet, as Biden's climate change plan demonstrated, even the most restrained candidates are offering no shortage of changes that would have been considered the vanguard of political plausibility in earlier cycles.

"I do think there's a bit of an arms race underway," says Matt Bennett, an executive vice president at Third Way, a centrist Democratic group.

This commitment to scale creates several obvious risks. One is that the cumulative cost of the Democrats' ideas will provide tempting targets for Republicans poised to portray them as "tax and spend" liberals or even "socialists" in the general election.

"They are trying to appeal to specific groups with these specific policies (but) when they make all these promises they run the risk of frightening taxpayers," says Glen Bolger, a partner in the Republican polling firm Public Opinion Strategies.

Republican pollsters (and, privately, even some Democrats) report that in focus groups voters are already expressing skepticism that all of the ideas the Democratic field is proposing, such as universal pre-K and expanded access to higher education, can be funded just by raising taxes on the wealthy, without touching the middle class.

"Swing voters understand 'free is not free' as a powerful way to capture the Democrat agenda," Public Opinion Strategies argued in a memo on public opinion that it released last week.

Yet many Democrats believe they will be shielded from those Republican arguments by the huge cost of the Trump tax cut: Its nearly $2 trillion price tag over the next decade means they can claim to fund big components of their agenda by retrenching it.

"One thing they have that Clinton didn't is the Trump tax cuts," Bennett says. "That is different, and that is a big pot of money they can spend."

The other big question posed by the scale of the Democratic agenda is how the candidates propose to move these ideas into law at a time when the country is so closely split between the major parties. Even if Democrats hold the House and win the White House next year, they are highly unlikely to achieve more than a very narrow Senate majority, under the most optimistic projections. That means even if they capture the majority, most of these ambitious Democratic ideas still would be subject to Republican filibusters.

Only a handful of Democratic candidates, particularly Warren and South Bend, Indiana, Mayor Pete Buttigieg, have committed to trying to eliminate the filibuster if they win the White House. (Trump has also called for eliminating it). Several of the senators in the race, including Sanders and Booker, have defended the filibuster, arguing that its termination would expose Democrats to unacceptable risks when they fall into the minority.

Besides, any Democratic Senate majority in 2021 would require at least some gains for the party in states that are closely divided between the parties or even lean toward the GOP, such as Alabama, Arizona, North Carolina, Iowa and Georgia. That means it's not guaranteed that even if Democrats eliminated the filibuster they would be assured of holding enough of their own caucus to amass a majority vote for their most ambitious ideas.

Moreover, it remains unclear that the public is as receptive as Democrats hope to the notion of providing Washington with sweeping new authority across a range of issues. While the share of Americans who say they would prefer a "bigger government with more services" has increased over the past several years in polling by the nonpartisan Pew Research Center , that number reached only 47% in the latest survey -- just as many Americans said they prefer "a smaller government with fewer services."

Can pragmatism win in 2020?

The debate over the viability of the most ambitious Democratic ideas is on track to unfold very differently this time than it did in the 2016 primaries. In that race, Clinton only rarely challenged the substance of Sanders' sweeping ideas . Rather, she mostly argued that plans such as his single-payer health care system were unlikely to pass a closely divided Congress.

In effect, she ceded the field of inspirational change to Sanders and presented her own ideas not as superior, but merely as more pragmatic. That left her in the position of seeming to rain on the party's excitement with dour, if accurate, warnings about the unlikelihood of Sanders' agenda ever clearing a closely divided Congress.

Even the most centrist Democrats seem conscious today of avoiding that trap. Given the fervor among the party's activist base for a strong response to Trump, Bennett says he thinks "there's a real danger" for any Democratic contender to make the Clinton argument that the field's most ambitious ideas are unlikely to pass.

From a different point on the party's ideological spectrum, Tanden agrees. "There is a question of level and scope," she says. "But ... I don't know that it is going to be successful, in a Democratic primary, to criticize Sen. Warren for doing so much, and I don't even know it's going to be effective in a general election."

One candidate who appears to have taken the Clinton precedent to heart is the front-runner, Biden. The former vice president generally hasn't embraced the field's most liberal positions. For instance, he's rejected a government takeover of the health care system and proposed instead to allow more Americans to buy into Medicare.

Biden's climate plan , though proposing a carbon-neutral economy by 2050, maintains a possible role for nuclear power and capturing the carbon from coal-generated electricity, ideas anathema to the most liberal environmentalists. Biden's aides say flatly that he won't be tempted into a "bidding war" with opponents who are constantly promising to spend more, or extend federal regulations further, on problems Democrats care about, from combating climate change to easing economic inequality.

But unlike Clinton, Biden is not centering his case against those ideas on the claim that they can't pass Congress; he's arguing instead that they are the wrong policy. On health care, for instance, he argues that shifting to a government-run system would be too disruptive to the roughly 180 million Americans with health insurance.

"We are developing a very bold, very progressive agenda that he thinks is the right way to go," said one Biden adviser, who asked for anonymity to discuss internal campaign deliberations. "He's not telling you, 'Guys, I've seen Washington. You're never going to get that done.' It's not, 'That would be great if only we could do it.' He's going to argue that his ideas are the right way forward."

Still, when the Democratic presidential debates begin later this month in Miami, many of the rivals surrounding Biden onstage will be promising more sweeping and expensive programs on a wide array of issues.

Sanders hinted at the arguments they will raise in his recent appearance at the California Democratic convention, when he repeatedly declared there could be "no middle ground" on issues from climate to abortion. "We cannot go back to the old ways," Sanders insisted, "we have got to go forward with a new and progressive agenda."

At the same event, Warren declared: "The time for small ideas is over."

Neither candidate mentioned Biden's name, but there was little doubt that their language referred to him. From the many candidates to Biden's left, those arguments are virtually certain to grow more pointed at the first debate, and at the CNN debate that follows in July.

Biden may be determined to avoid a bidding war in his policy promises, but like all battle plans, it's an open question whether that strategy can survive first contact with the enemy.