The effect is immediate, boosting a particularly distressed economic sector. The principal beneficiary lives on Main Street. And there is collateral environmental benefit.

This describes the "cash for clunkers" program, a model for what taxpayers should expect from federal economic stimulus. Its only flaw, it seems, is that it is wildly successful. So much so that it is in danger of running out of money. It shouldn't be allowed to.

The White House offers assurance that it won't, and the House on Friday voted for an extra $2 billion. The Senate had yet to act.

Not to belittle the value of rescuing financial markets, but it's often hard for the public to discern the immediate benefit of bailing out Wall Street titans. This is all the more difficult when employees who helped take these firms to the brink of implosion get bonuses. But it is a particularly difficult sell simply because Joe Six-Pack is wondering where that trickle-down effect has trickled off to.

There is no such confusion with the "cash for clunkers" program. It works this way:

Got a vehicle that gets 18 mpg or fewer? You can get a tax credit of up to $4,500 on the purchase or lease of a new, better-mileage vehicle. The Car Allowance Rebate System program started Monday. It was to have lasted until Nov. 1 or as long as the money held out. That, it turned out, was about four days.

Here at least are instant consumer dollars spent, dealers on up to autoworkers benefitting. Moreover, fewer low-mileage cars are on the road, replaced with cleaner and more fuel-efficient vehicles.

Yes, extend the program. Also, as a letter to the National Highway Traffic Safety Administration signed by Wisconsin Democratic Sen. Russ Feingold suggests, waive the rule that requires the clunkers to have been insured for a year before being traded in. Wisconsin's new mandate for auto insurance begins June 1, 2010.