In the ongoing battle of the budget, President Obama has done something very cruel. Declaring that this time he won’t negotiate with himself, he has refused to lay out a proposal reflecting what he thinks Republicans want. Instead, he has demanded that Republicans themselves say, explicitly, what they want. And guess what: They can’t or won’t do it.

No, really. While there has been a lot of bluster from the G.O.P. about how we should reduce the deficit with spending cuts, not tax increases, no leading figures on the Republican side have been able or willing to specify what, exactly, they want to cut.

And there’s a reason for this reticence. The fact is that Republican posturing on the deficit has always been a con game, a play on the innumeracy of voters and reporters. Now Mr. Obama has demanded that the G.O.P. put up or shut up — and the response is an aggrieved mumble.

Here’s where we are right now: As his opening bid in negotiations, Mr. Obama has proposed raising about $1.6 trillion in additional revenue over the next decade, with the majority coming from letting the high-end Bush tax cuts expire and the rest from measures to limit tax deductions. He would also cut spending by about $400 billion, through such measures as giving Medicare the ability to bargain for lower drug prices.