President Barack Obama rolled out a $3.7 trillion budget Monday that promises $90 billion in reduced spending for fiscal 2012, but it still would produce a whopping $1.1 trillion deficit.

The best that can be said is that we’ve started to frame the national debate. The president wants to spend $3.7 trillion. There’s your top line.

Republican leaders are pressing the White House for deeper cuts. There’s your second line.

Republican members are pressing their leaders to go even lower. There, somewhere, is your bottom line for 2012.

And even that won’t be enough.

The debate over fiscal responsibility in the months ahead will deal only with a slim portion of federal spending. Nobody in power — not Obama, not the Demo-crats who run the Senate, not the Republicans who run the House — wants to talk much about what it’s going to take to curb the huge projected growth in entitlement spending. Even Obama’s projections say deficits will fall only to $607 billion a year by 2015, but will start rising rapidly again.

Remember what the president’s deficit commission said just a few months ago? The bipartisan group returned a report full of straight talk. We need to raise the retirement age for Social Security. We need to put federal health care programs on a strict diet. We need to slash defense spending. We need to cut tax rates and at the same time eliminate cherished tax breaks that distort the economy, such as mortgage-interest deductions.

Those deficit reduction measures and others backed by a majority of the commission members would save $3.9 trillion over the coming decade. The president’s budget would reduce the deficit by only $1.1 trillion.

The big difference: Obama targets relatively small game. The administration seems to think that its commitment to reducing the deficit would be fulfilled by steps such as cutting $300 million from community development block grants.

True, Obama and other Demo-crats hold those block grants dear. In the context of our fiscal problems, however, they’re tiny. Senate Budget Chairman Kent Conrad of North Dakota, a Democrat, admitted as much: To whittle the debt down to a sustainable level, he said Monday, “We’ve got to do substantially more. . . . We just do.”

House Republicans have promised to go deeper, but they have not been willing to set out plans for specific entitlements on the order of what the deficit commission recommended.

We know that’s hard. People want Congress to stop spending, but they’re not too wild about hearing it might squeeze their health care or their retirement.

It was all fine and good for Republicans and Democrats to sit next to each other at the State of the Union address. Here’s what they really need to do. They need to grab each other’s arms, hold each other up, tell the American people what it really will take to return the federal government to fiscal balance.

And do it. Then they can make a grand bipartisan shudder as the public screams. But they have to do it. They have to.