It didn't surprise me that Sen. Bernie Sanders chose this moment to press for a single-payer health system.

He's a good man, and he's dead right that a single-payer system like Canada's makes a lot of sense, delivering better care at lower cost. But he is as nutty as Ralph Nader when it comes to practical politics.

Sanders is handing Republicans a club they can use to beat Democrats over the head. Because a single-payer system would require a huge tax hike, and force wrenching change for everyone at a time when 70 percent of Americans are happy with their current arrangements.

Sanders has never been impressed by cold political calculations like that. That's why he ignored warnings that his endless personal attacks on Hillary Clinton might help Donald Trump win by depressing the Democratic vote in the general election.

Sanders, like Nader, is a romantic. Which is great, if you're a poet.

The surprise to me is that our own Sen. Cory Booker has joined this hapless parade.

"We have to stop thinking about political calculation," he told me on Friday morning. "And focus more on 'Morally what's the right thing to do?'"

Uh-oh. Has Booker been infected by the Sanders virus?

The idea that answering moral demands should force us to set aside political calculation is insane. Without political calculation, Abraham Lincoln could not have won the Civil War and freed the slaves. Franklin Roosevelt couldn't have enacted Social Security. Nelson Mandela might have died in his cell on Robben Island.

None of them charged straight at their goals. They maneuvered towards them, step by step, over years. They calculated.

Booker knows that, of course. Republicans run the Senate, and he has calculated that he must compromise with them to get anything done. So he's teamed up with Sen. Rand Paul (R-Kentucky) on criminal justice reform, and with Sen. Tim Scott (R-S. Carolina), on job training.

"I will work with anyone, from any party, to make a difference for the people of New Jersey," he said during his rookie year in the Senate.

So why is he now talking smack about the evils of political calculation?

The irony is that it's another calculation. He needs to spout off like this to stay in the running as possible candidate for president, or vice-president. He needs to dance for the die-hards who love Bernie.

And the left is skeptical about Booker, thanks largely to his cozy ties with Wall Street, his second-largest source of campaign money, behind lawyers.

It's not just the money. In 2012, when President Barack Obama's campaign was hammering Mitt Romney as a bloodthirsty capitalist, Booker went way off message on national TV.

"I'm not going to sit here and indict private equity," he said on NBC's Meet the Press. "If you look at the totality of Bain Capital's record, they've done a lot to support businesses to grow."

It's a silly knock on Booker. He supports Wall Street reform, and the attacks on Romney were indeed unfair. But in both parties, the base operates by a strict and unforgiving code.

When I surveyed Republican primary voters in Iowa last year, the biggest complaint I heard about Gov. Chris Christie, by far, was that he hugged Obama after Hurricane Sandy.

The Democratic base is not that nutty, but it is demanding. Even after Booker stood with Sanders this week, the head of MoveOn.org, Ilya Sheyman, demanded more.

"No one issue or position is enough to establish progressive credentials," he told Roll Call magazine.

The truth is Booker is not an orthodox Democrat. He was once an avid supporter of school vouchers, which allow students to use public money for tuition at private schools, even Catholic schools. As mayor in Newark, he shrunk the city workforce by about one-quarter, a record of austerity no other mayor can match, even Republicans.

I've always liked that about him, and given his unmatched popularity in New Jersey, it seems most voters agree.

So, here's praying that Booker's detour into Bernie-land is just a romantic weekend, not a real thing.

Don't get me wrong: If I could pull a switch, and trade health systems with Canada, I'd do it in a minute. Ours is the most savage system in the advanced world, and the most expensive. Obamacare got us about halfway to where we need to go.

Democrats should press for steps to improve it, like more generous subsidies, or a public option on the exchanges, or another expansion of Medicaid. They should support a bill that would allow people over 55 to buy into Medicare. Each move would bring us closer to a single-payer system without all the political risk of this wild leap.

Sanders notes that some credible polls show America wants a single-payer system, and that's true. A June poll from the Kaiser Family Foundation found 53 percent support, up from 50 percent last year.

But it also found that Republican arguments against it would be potent. When respondents are told that taxes would rise, 60 percent oppose single-payer. When they are told it would give government control over health care, 62 percent oppose it.

Booker argues that while taxes would increase under this plan, health costs now paid in the private sector would drop even more, creating a net savings and allowing employers to hike wages.

That's probably true if we executed it as well as Canada, but this is a skeptical age. A big tax hike would be the sure thing.

I asked Booker how a massive tax hike would play politically. "People should stop looking at buzz words like you're using, and ask themselves, 'Will I be better off?'"

Maybe they should, but they won't.

This exercise isn't really about health care, anyway. It's about presidential politics, about the 2020 election already making people a little crazy. Even Booker.

I asked him flat out if he intends to run. "I'm not even thinking about that," he said. "It's not on my radar."

That, of course, is what he must say to avoid sounding like an arrogant young senator. My guess is that Booker made that calculation, and chose to lie, for good reason.

Maybe he's no Bernie Sanders after all.

More: Tom Moran columns

Tom Moran may be reached at tmoran@starledger.com or call (973) 836-4909. Follow him on Twitter @tomamoran. Find NJ.com Opinion on Facebook.