While the first Democratic presidential debates were clearly not scheduled to coincide with the release of the Congressional Budget Office’s 2019 long-term budget outlook, their contemporaneous timing was instructive on many levels.

At a time when the Democratic Party is moving further to the left, with candidates competing with one another to see who can offer the most “free stuff,” the CBO is warning about unsustainable tax-and-spend policies in the face of what is likely to be an extended period of slower economic growth.

The real risk to Democrats at this stage, however, is that, if adopted as part of the party platform for the 2020 election, their progressive policy proposals will be rejected by moderate Democrats and independents, ensuring four more years of President Donald Trump.

What are some of the social and economic policy initiatives many of the candidates are calling for? Tuition-free college, free child care, the cancellation of student-loan debt, single-payer health care, a guaranteed basic income: all paid for with higher taxes.

Inadequate funding

It is unlikely that those taxes, including Massachusetts Sen. Elizabeth Warren’s proposed wealth tax, which is certain to prompt a constitutional challenge, will be adequate to pay for their expensive promises, according to experts.

Reviews of the wealth taxes implemented by 15 European Union countries found that determining the value of assets was difficult, administering the tax was expensive, and cheating was easy.

What’s more, “the revenues collected from net wealth taxes have also, with a few exceptions, been very low,” according to a 2018 analysis by the Organisztion for Economic Development and Cooperation.. Which is why most of those countries eliminated the wealth tax.

The Democrats’ proposed new spending comes at a time when the federal government’s fiscal position has deteriorated due to high and rising debt, even in the face of a decade-long expansion. Here are some of the highlights from CBO’s latest report, released last week.

• The annual budget deficit is expected to rise from 4.2% of gross domestic product in 2019 to 8.7% in 2049 as spending outpaces revenue;

• Rising deficits will boost federal debt held by the public from 78% of GDP in 2019 to 144% by 2049;

• The sources of the expected increase in outlays are health care programs, social security and net interest on the debt, all of which are on automatic pilot.

Fashionable views

While it has become fashionable in some economic circles to dismiss rising debt as a risk factor — Hey, look at the ultra-low interest rates in the face of ballooning debt! — CBO doesn’t share that optimism, arguing that rising debt “would dampen economic output over time” by crowding out productive private-sector investment.

In a new working paper, “Fiscal Space and the Aftermath of Financial Crises: How It Matters and Why,” economists Christine D. Romer and David H. Romer argue that highly indebted nations have less “space” to respond to financial crises, auguring a greater loss of economic output and a slower recovery.

At the same time debt is rising, potential growth is falling, a function of sluggish labor force and productivity growth. So the dual whammy of rising debt and lower output is not exactly an ideal backdrop for introducing expensive experiments in social policy.

To be sure, most of the Democratic candidates did not raise their hands when asked on stage if they would eliminate private insurance and replace it with Medicare-for-all, an idea popularized by Vermont Sen. Bernie Sanders.

Minnesota Sen. Amy Klobuchar, for example, one of the handful of moderates in the Democratic field, advocated for a less disruptive “bold idea”: creating an optional public plan instead of “kicking half of America off their health insurance in four years.”

More than half of Americans under the age of 65, or about 158 million people, get health insurance through their employer. They weren’t happy when they learned that, contrary to assurances, under the Affordable Care Act they could not keep their doctor even though they liked their doctor. (The popularity of the ACA increased with threats to take it away.) Imagine how they would feel if their health insurance plan is eliminated.

Moderates flipped the House

In the 2018 midterm election, Democrats picked up congressional seats and won the governorships in Michigan, Wisconsin and Pennsylvania, three states that threw the Electoral College to Donald Trump in 2016. They didn’t flip the House of Representatives with a slate of progressive candidates. They won with moderates who appealed to white, working-class voters.

If the Democrats want to unseat Donald Trump in 2020, they are not going to do it with an expensive progressive policy agenda. (There’s plenty of time for that once they take control of the White House and Congress, right?)

On the second night of last week’s debate, eight of 10 Democrats raised their hands in support of decriminalizing illegal border crossings, an idea that will alienate some swing voters and leave the Democrats open to Trump’s accusations that they favor open borders.

This is not the route to victory in 2020. A large majority of registered voters who identified as Democrats or Independents said the most important priority was nominating a candidate who has the best chance of defeating Trump, not issues.

So your call, Democrats. Everything in moderation? Or California Dreamin’ followed by a crash landing?