Today Barack Obama is having lunch with Congressional Republicans in a meeting that Congressional Quarterly says may be historic. He is trying to drum up support for his economic stimulus package — which today sits at $825 billion or so, and growing. If he is politically shrewd — and experience suggest that he is — he’ll try to erase memories of his “I won” moment last week by promising to press Nancy Pelosi and Harry Reid to include some Republican idea(s) in the package before it’s sent to him. If so, some Republicans are bound to back the proposal.

But Republicans need to step back from the current debate and look at the broader picture. This is not the last big ticket item from the Obama administration this year. We know that there will be a proposal for health care reform, which is likely to cost the taxpayers hundreds of billions of dollars. There will be a new 5-year (more or less) transportation bill to replace SAFETEA-LU. The new package could total $500 billion or more. There is talk of a TARP II, which might cost another trillion dollars or more. There may be an entitlement reform bill. There will likely be an energy bill — if only to implement a costly cap-and-trade system to ration energy. There may be a few more big ticket items not yet included on the list. And that doesn’t even address typical ‘small-ticket’ items whose cost is measured in the tens of billions rather than hundreds (such as SCHIP).

All told, the Obama administration could easily request more than $2 trillion in additional spending this year — above and beyond the normal $3 trillion federal budget.

Any rational Member of Congress would insist on getting some idea of the total ‘ask’ before voting on one large chunk of it. Republicans should insist on it. Is this $825 billion package 70 percent of the eventual total request, or 30 percent? How much more will the president want for transportation, health care, water quality, superfund, national defense, education, criminal justice, and a whole host of other programs, above and beyond what is included in the current package? It’s obvious that the risky spending scheme before Congress today is a bad bill — a collection of left-over spending requests from earlier years, cobbled together in the name of stimulus. And it will do nothing to create good-paying, lasting jobs.

But especially for Members who might be thinking of voting for it, they should insist that the president come through with some of his famous ‘openness and transparency’ and tell them how much more he’ll request later. It should not be too hard. After all, Obama has promised the Congressional Blue Dogs that he will convene a budget summit in the near future to begin figuring out how to bring the deficit down in the future. Therefore he must have a pretty good idea of what the overall spending picture looks like.

When Republicans meet with Obama today, they should ask Obama about his future spending plans. The answer is critical to putting this and other votes in context.