Democrats have spent this term in Green Neverland daydreaming about what cars automakers should build in order to save the planet and themselves. Detroit “must build the cars of the future” our president likes to say. But with Washington now finding itself an investor in the most complicated consumer-products business on the planet, politicians are being forced to face reality.

Take this week’s House effort to draft a “cash for clunkers” bill modeled after European “scrappage” incentives for consumers to trade in their old cars for new models, thus jump-starting dead car sales.

Loath to let a crisis go to waste, Democrats added green provisions to force consumers to consider only fuel-efficient cars. Two bills emerged from this process, with green groups favoring a proposal sponsored by Rep. Steve Israel (D., N.Y.) requiring that eligible cars for purchase get a whopping 25 percent more than current fuel mileage rules, or 34 mpg for cars and 28 mpg for trucks. (A competing bill from Rep. Betty Sutton (D., Ohio), supported by the Michigan delegation, would extend the deal to American cars only — a measure protested for its protectionist trade implications).

Well, hello, reality. While Congress fancies the idea that Americans crave small cars, they don’t. The number of vehicles that meet the Israel bill criteria is small — and they are small cars, so-called B or C-class cars like the Toyota Yaris or hybrids like the Toyota Prius. As a result, the bills would have discriminated against families that need larger vehicles and ultimately would have done little for Detroit because the mpg designation would bypass the D and E class segments which are the meat of auto sales. For example, Chrysler — the hardest-hit automaker — would have no vehicles qualify.

As a result, a compromise reportedly reached Wednesday between the two bills departs significantly from their original, green priorities. Charles Territo of the Alliance of Automobile Manufacturers says dryly: “Members of Congress are getting much more insight into the vehicles that consumers want.”

Gone are the hard ideological demands that a voucher worth $3,000 to $5,000 go only to small cars — replaced by rules that echo existing federal CAFE rules of 22.7 mpg for trucks 27.5 mpg for cars, averages that every major manufacturer meets.

Furthermore, Rep. Israel indicated that the standards would be soft, requiring the purchase of vehicles “at or near existing CAFE standards.” In other words, a loophole you can drive a Chrysler Town & Country minivan (21 mpg) or GMC Canyon Crew Cab pickup (21 mpg) through.

“It’s a disappointing compromise,” Israel said, trying to appease outraged green groups. “It isn’t exactly visionary.”

No, but it’s a nod to reality.