To build support for a border fence, legislators needed only one item — pandering on an issue that did nothing but provide red meat for their base. But to build the fence, the lawmakers needed two more items — legislation and funding. They got the legislation — the president signed the bill authorizing construction of the fence last fall — but if they yell, "Show me the money," they might not like the answer. President Bush addressed the fence in his budget, but of the $2.9 trillion he proposed, a tiny fraction, $1 billion, would go into the very barrier...