When you get right down to it, the jobs plan President Obama proposed before a joint session of Congress last night was built on three elements:  A large payroll tax cut, lots of new spending on public infrastructure, and a promise that its $447 billion cost would be paid for with yet-to-be disclosed tax hikes and spending cuts. As political theater, the speech was terrific. It was a powerful defense of government—words his base has been longing to hear since the 2010 election. It challenged Republicans to “stop the political circus” and work with him to boost the economy—a poll-tested argument that appears to have strong support among many Americans. And the often dispassionate president sounded as if he really cared. As substance, his plan, called the American Jobs Act, combines the bold with small-bore, Bill Clinton-like subsidies for carefully selected interests. Mixing short-term stimulus with long-term deficit reduction is perfectly sensible. But did Obama get the right mix? By far his most ambitious idea is to extend through 2012 and expand the payroll tax cut that was due to expire at the end of this year. His plan, which would reduce federal revenues by $170 billion, would cut the worker share of the payroll tax to 3.1 percent from 4.2 percent (it was 6.2 percent prior to this year’s tax holiday). At the same time, it would cut the employer share to 3.1 percent from 6.2 percent on the first $5 million of payroll. Firms that add workers or give current employees raises would pay no wage tax on up to $50 million in new payroll. On the spending side, Obama would give $85 billion to state and local governments to, among other things, build and repair schools and hire (or rehire) teachers, spend $50 billion on transportation, create a $10 billion infrastructure bank, and spend $55 billion to extend unemployment benefits for another year and otherwise  help the long-term jobless. At the same time, the plan is filled with promises that have political pizazz—extra tax breaks for companies that hire veterans, the long-term unemployed, low-income youth, and first-responders—but many are warmed-over ideas he’s proposed before. Finally, he promised to help Americans refinance their mortgages. This could prove to be the most important step of all, except he offered no real plan. What would all this do for the economy? It would help some, but even if Congress did pass it, don’t expect magic. Extending and expanding the worker payroll tax cut will continue to put cash in people’s pockets-- as it did this year. At the very least, continuing the tax break won’t shrink consumer demand, which might happen if the payroll tax break is allowed to expire at year's end.  It isn’t likely to create many new jobs, however. With much of the recent job loss caused by state and local government layoffs, renewed aid to states will help some.  More infrastructure spending is necessary but, as we learned over the past few years, a lot fewer of these projects are “shovel-ready” than Obama once hoped.  It may take a while for those bucks to work their way through the economy. The tax breaks for companies that hire vets and the like probably won’t increase hiring at all. It will encourage firms to employ targeted workers, but at the expense of those who are not on the preferred list. The payroll tax cut for employers may also help some, but not much. And many profitable firms will enjoy a windfall for hiring workers they would have hired anyway. Finally, while Obama vowed to pay for all of this over the long-run, he didn’t say how. That will be left, he said, for the coming days. In the long-run, the way he fills in those blanks will be as important as what he said last night. When you hire Carnegie Hall, you better put on a blockbuster show. President Obama raised expectations by delivering his jobs plan to a joint session of Congress. He delivered a strong performance. But we still don't know if his plan will be as impressive as his rhetoric.