Last week two Congressional Democrats, Rep. Alexandria Ocasio-Cortez and Sen. Ed Markey, unveiled their Green New Deal. The resolution claims that environmental and economic conditions require the federal government to take drastic action, such as updating or replacing every building in the country and guaranteeing jobs to all Americans. The proposal has been described as “the same old socialist hooey,” and even many Democrats consider it unfeasible.

Senate Majority Leader Mitch McConnell announced yesterday that he wants the Senate to vote on the resolution. “I’ll give everybody an opportunity to go on record and see how they feel about the Green New Deal,” said McConnell.

McConnell seems to think he’s going to embarrass Congressional Democrats by showing they’re out of sync with voters. But what he may be showing is that he doesn’t fully understand why we’re even talking about the Green New Deal in the first place.

Those who are proposing the Green New Deal recognize that it’s radical. Indeed, that’s the point. As Megan McArdle explains,

Progressives frequently argue that getting to “as much as possible” requires setting goals that are out of reach. They call it “shifting the Overton window,” or widening the spectrum of plausible policy options, an idea broached in the 1990s by policy analyst Joseph P. Overton. The folk version: Ask for the stars, you’ll get the moon.

The Overton Window describes a “window” in the range of public reactions to ideas in public discourse. Overton believed that the spectrum included all possible options in a window of opportunity:

Imagine, if you will, a yardstick standing on end. On either end are the extreme policy actions for any political issue. Between the ends lie all gradations of policy from one extreme to the other. The yardstick represents the full political spectrum for a particular issue. The essence of the Overton window is that only a portion of this policy spectrum is within the realm of the politically possible at any time. Regardless of how vigorously a think tank or other group may campaign, only policy initiatives within this window of the politically possible will meet with success.

All issues fall somewhere along this policy continuum, which can be roughly outlined as: Unthinkable, Radical, Acceptable, Sensible, Popular, Policy. When the window moves or expands, ideas can accordingly e more or less politically acceptable.

Politicians are necessary to move an idea into the last phase—policy. But it’s a misunderstanding of the process to think that politicians are driving the shift.

“The mon misconception is that lawmakers themselves are in the business of shifting the Overton window,” says Joseph Lehman, a colleague of the late Overton. “That is absolutely false. Lawmakers are actually in the business of detecting where the window is, and then moving to be in accordance with it.”

In other words, politicians respond to the public’s definition of the window, not the other way around. McConnell seems to think the Green New Deal is a bizarre proposal that has no constituency. But as NPR notes, there are 67 co-sponsors in the House and 11 in the Senate, including several current or potential presidential contenders: Bernie Sanders, Kirsten Gillibrand, Elizabeth Warren, Cory Booker, and Amy Klobuchar.

The reason so many Democratic presidential candidates support a bizarre plan like the Green New Deal is not that they themselves believe in it (though many do) but that they know many of their voters (especially primary voters) support the proposal. Politicians aren’t know for their bravery or forward-thinking. If they are ready to support a position it is because they think there is a substantial and vocal portion of the electorate that has already shifted the Overton Window to a point where it has the potential to e policy.

That is why conservative Christians can no longer mock and shrug when a politicians endorses an idea—such as infanticide or socialism—that we believe has been relegated to the dustbin of history. Progressive activists are constantly moving the Overton Window in disturbing ways. By the time we see progressive politicians nodding along in agreement, we’ve already reached a tipping point where the “Unthinkable” may soon e “Policy.”