Sen. Kamala Harris of California may have been the breakout winner of this week’s Democratic presidential debates, but there was one clear loser: the American taxpayer. These were the most expensive presidential debates in American history. Never have so many candidates proposed to spend so much.

In the first debate, NBC anchor Savannah Guthrie asked Massachusetts Sen. Elizabeth Warren about the economic impact of her plans for “free college, free child care, government health care, cancellation of student debt” and in the second asked Sen. Bernie Sanders, I-Vt., whether his proposals “for big, new government benefits, like universal health care and free college,” would require middle-class tax increases. (They would.)

But no one asked any of the candidates a simple question: How much is all of that going to cost?

Instead of shoring up Medicare, Democrats want to expand it to cover virtually everyone in the country. Sanders’ “Medicare for All” legislation has been co-sponsored by Sens. Warren, Harris, Cory Booker of New Jersey and Kirsten Gillibrand of New York. Nonpartisan estimates put its cost at $32 trillion over the first 10 years.

Or take free college. Harris, Warren, Gillibrand and Booker have signed on to the Debt-Free College Act, which would cost at least $840 billion over 10 years. Sanders has introduced a $2.2 trillion College for All Act that would make public colleges and universities tuition-free and debt-free, and erase the roughly $1.6 trillion in student loan debt. Warren has also proposed a $640 billion student loan debt cancellation plan.

Warren has proposed a plan for “universal child care” and early learning that would cost $700 billion over 10 years, while Harris, Beto O’Rourke and Rep. Eric Swalwell, D-Calif., have endorsed the Child Care for Working Families Act, which would cost $700 billion over 10 years..

Amazingly, none of the NBC anchors asked about the Green New Deal, but climate change was front and center in both debates. Joe Biden’s climate plan would cost $1.7 trillion over a decade. Warren has pitched a $2 trillion plan, O’Rourke’s proposal would cost $5 trillion, while Washington Gov. Jay Inslee’s green-jobs plan would cost $9 trillion.

Then there are government-guaranteed jobs. Harris, Warren and Gillibrand have all co-sponsored Booker’s Federal Jobs Guarantee Development Act, while Sanders has proposed an ambitious government jobs plan with guaranteed wages of $15 an hour, retirement and health benefits, child care and paid family leave. None have explained how much their plans would cost, but the liberal Center on Budget and Policy Priorities put the cost of even a less ambitious guaranteed-jobs plan – covering just 9.7 million workers – at $6.8 trillion over the next decade. Andrew Yang proposed a government-provided universal basic income that would give every American over the age of 18 a monthly check of $1,000 – which would cost between $28 trillion and $40 trillion over 10 years.

Add it all up, and it’s enough to make a Soviet central planner blush.

But where things get really expensive is the nexus between the Democrats’ spending plans and their immigration policies. During the first debate, former Housing and Urban Development Secretary Julián Castro said he would decriminalize illegal border crossings. When the candidates in the second debate were asked how many supported his plan, nearly every candidate’s hand went up. (Sen. Michael Bennet of Colorado was the only one to abstain.) Every candidate raised a hand when asked if their government health plan would provide coverage for illegal immigrants.

The combination of decriminalizing illegal entry and offering those who enter illegally free health care would create a magnet for millions to enter our country – dramatically increasing the cost of every public health care plan. And once here, these migrants would presumably also seek to take advantage of other free programs the Democrats are proposing, which means their costs would also skyrocket beyond these estimates.

Open borders and socialism are a path to national suicide. According to the Congressional Budget Office, under current law – without all the Democrats’ new entitlements – debt held by the public is already projected to increase from 78 percent of gross domestic product today to 144 percent by 2049. This level of debt is unsustainable and could lead to another financial crisis.

But no worries, New York Mayor Bill de Blasio assured us that “there’s plenty of money in this country. It’s just in the wrong hands. Democrats have to fix that.”

I’m sure they will.

Washington Post columnist Marc A. Thiessen is a fellow at the American Enterprise Institute and former chief speechwriter for President George W. Bush.

Twitter: marcthiessen