It was arguably the line of the night.

And in case you happened to miss it, Sen. Elizabeth Warren wanted to make sure she emphasized its significance, so she tweeted it after.

“I genuinely do not understand why anyone would go to all the trouble of running for president just to get up on this stage and talk about what’s not possible.” Warren delivered the line, to huge applause, well into the first night of the Democratic debates on CNN, after taking some pretty serious incoming from a number of her more moderate opponents.

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Montana Gov. Steve Bullock, making his first debate appearance and boasting of his red-state electability, referred to some of Warren and Bernie Sanders’ progressive proposals as “wish-list economics.”

Former Colorado Gov. John Hickenlooper argued that the guarantee of a government job in the progressive-backed Green New Deal “is a disaster at the ballot box,” warning, “You might as well FedEx the election to Donald Trump.”

Former Maryland Rep. John Delaney pounded the progressives for “fairy-tale” ideas like Medicare for All, saying, “We don’t have to go around and be the party of subtraction, and telling half the country who has private health insurance that their health insurance is illegal.”

Likewise, Ohio Rep. Tim Ryan scolded Warren and Sanders for “taking private health insurance away from union members in the industrial Midwest,” decriminalizing the border, giving health insurance to undocumented workers and ignoring “working-class issues,” those most important to “the people that take a shower after work who haven’t had a raise in 30 years.”

In other words, the moderates fought back on Tuesday night. But, as she’s wont to do, Warren had a plan for that, which was, essentially, to call them all scaredy-cats.

Early on, she called out her Democratic opponents who have refused to follow her and Sanders on their far-left crusade. “We’re not going to solve the urgent problems that we face with small ideas and spinelessness,” she reprimanded. She chided them for lacking the political will to fight for big ideas, to think as boldly as she was, and for worrying about little things like electability.

She may as well have said to Ryan, Delaney, Bullock and Hickenlooper, “Where’s your manhood?”

But while it may have made for good theater, the line — questioning why anyone would go to the trouble of running just to talk about what they can’t do — also highlights the central dilemma for the Democratic field.

Do they just want to run or do they want to win?

It’s worth noting, however obvious, that the point of going to all the trouble of running is still, in the end, about winning the damn thing. It’s about beating President Donald Trump and ending his reign of division, fear mongering, otherism and bigotry.

The stakes are high, and he’ll be hard to defeat.

Candidates who are asking whether certain policies are too far left, unpopular, impractical and unelectable aren’t weak or impotent; they’re strategic and realistic. (Never mind the question of whether particular policies can then get through a Congress that’s likely to be divided if they manage to win; remember, the Affordable Care Act barely squeaked through.)

Many on the left are worried that Warren and Sanders are pulling the field too far just for the sake of progressive bragging rights. Thomas Friedman in The New York Times pleaded with Democrats, writing “Please, spare me the revolution! It can wait. Win the presidency, hold the House and narrow the spread in the Senate, and a lot of good things still can be accomplished.”

Hickenlooper reminded debate watchers that many of the progressive policies Warren and Sanders are proposing were not supported by the moderate Democrats who helped flip the House in 2018.

Maybe for Warren, they just weren’t brave enough or macho enough to run on really big ideas — but at least they got the win.

My colleague Van Jones tried to frame it in less goading terms than Warren. “For progressives, electrifying ideas = electability. Why can’t we be audacious? Why can’t we fight for what we believe in?” he tweeted after the debate.

Progressives can be audacious, but it comes with consequences.

See Franklin D. Roosevelt and his losing proposal to stack the courts. See the 1994 assault weapons ban, after which Democrats promptly lost 54 House seats. See George W. Bush’s Iraq war.

All that audacity proved perilous for their parties.

President Barack Obama, for all the criticism from conservatives that he would turn America into a socialist dystopia, understood the value of incrementalism, whether on health care, immigration, gun control or myriad other issues. Many Democrats bemoan his caution, but his lack of audacity probably helped him get elected, twice.

Warren is an effective bully. Inciting and provoking her opponents to man up and stop whining about what isn’t realistic will play well to the progressive base. It may even convince some Democrats that playing it smart is just playing it safe.

But asking whether ideas are unwinnable isn’t a sign of timidity or impotence; it’s actually the whole ball game.

S.E. Cupp is the host of “S.E. Cupp Unfiltered” on CNN.

Email: secuppdailynews@yahoo.com