The ultimatum has been delivered — and with it, Senate Minority Leader Mitch McConnell has delivered the political high ground to President Obama. Now, the president can force a showdown over federal spending, the threatened shutdown of government, and Tea Party demands to prevent an essential increase in the national debt ceiling.

McConnell's misstep was to acknowledge the Republican Party's determination to cut Social Security, Medicare, and Medicaid. If Obama won’t join the GOP in defacing and degrading these greatest legacies of the New Deal, the New Frontier, and the Great Society, McConnell insisted, then Republicans won’t agree to an increase in the debt limit — a decision that could bust financial markets and send unemployment rates soaring. It would be terra incognita — the strongest economy on earth shredding its own credit and credibility, creating an economic meltdown with fallout that lasts years or decades.

Opposing an increase in the debt ceiling is popular in the polls right now because Americans don’t understand the consequences. Once they became painfully clear, the politicians responsible would pay the price.

That’s why this can’t happen — unless it does. For Republicans to risk the possibility contradicts their self-proclaimed posture as the party of American exceptionalism — unless they mean that this nation should now become the exceptional great power, the only one in history to consciously embrace impotence, paralysis, and default.

This is a Tea Party idea — if you can dignify the insanity by conceding it any defensible intellectual content. One thing it’s certainly not is a genuinely Republican idea. Under Ronald Reagan, the paladin in name but not substance of today’s conservatives, the debt limit was raised regularly — three times, in fact, and by 100 percent in 1985.

The McConnell threat is also a dumb idea, even dumber than Newt Gingrich’s twin proposals to cut Medicare for seniors by $270 billion while simultaneously cutting taxes primarily for the wealthy by $250 billion — for which he was willing to close down the government in 1995.

At that time, President Clinton stood his ground: He was ready to veto both the tax cut and the Medicare cut. He and the Democrats had the political high ground, and Gingrich and the Republicans got the blame for closing the government for the sake of plutocracy and pique: Newt had been assigned to sit in the back of Air Force One on the flight to the funeral of assassinated Israeli Prime Minister Yitzhak Rabin.

McConnell hasn’t whined about not being served tea, in a cup or in concept, at the White House. But politically he’s concocted an even more lethal policy brew than Gingrich ever dared; he’s added Social Security to the mix.

This sets the stage for Obama, who’s been criticized so far for being disengaged during the early budget skirmishes. It’s the same criticism he usually confounds – that he was too far behind Hillary Clinton in the fall of 2007 for his message of change to catch fire — which it did in the Iowa caucuses; or that health reform was lost and he had to settle for a token bill; or that he had frittered away the chance to repeal “Don’t Ask, Don’t Tell.” This time, on the budget, there’s been a method and a dividend to the president’s apparent passivity. He hasn’t gotten in the way of an impending GOP train wreck, as the congressional party fractures between the convinced right and the crazy right. With the attention focused on Republican antics — from Wisconsin’s union busting to Washington Republicans happily proclaiming the virtues of a shutdown — twice as many Americans would now blame them, not Obama, if one occurs, according to a new Washington Post/ABC poll. Two weeks ago, blame was evenly divided.

This shift in public opinion took place at a time while the budget debate remained abstract, far more a question of cutting per se than of what was being cut. This should have favored the GOP, the deficit creators seen, fairly or unfairly, as the more fervently anti-deficit party. That the trend went the other way points to the scope of the opportunity McConnell has just handed Obama. 

Soon the President will no longer be quiet, and he has an argument to make that’s vivid, powerful, and simple: “I won’t be blackmailed into cutting Social Security, Medicare, and Medicaid.” And he can add in education — an area where the House Republican budget would decimate everything from Head Start to the Pell Grants that enable middle-class students to attend college. The contrast in budget proposals aligns perfectly with the President’s overall message: We want to win the future; they want to destroy the future. But now he has not just the slogan, but the proof — and by making the choices real and concrete, he can define the terms of the budget battle on the most favorable conceivable grounds.

Indeed, the public rejects every major GOP “fix” on Social Security. Americans know the fix is in — for Wall Street — when it comes to privatizing the program. The support for that is derisory in virtually every survey. Majorities in the latest Wall Street Journal/NBC poll, often overwhelming majorities, oppose raising the Social Security tax or the retirement age, reducing benefits for future retirees, or even an additional reduction for people who retire early. The one measure that the public favors – with a decent margin of 10% — is raising taxes on the wealthy by lifting the $107,000 ceiling on income subject to the payroll tax. I don’t think that’s what Mitch McConnell has in mind. And I can’t wait to see what horrors he has in store for Medicare. (What about, say, death panels, or rationing?)

One thing I am sure of: If the president wages this fight, the seniors who voted heavily Republican in the midterm elections won’t be making that mistake in 2012. And it’s not just seniors but voters across the board. Even before reaching the brink of a shutdown or debt-ceiling crisis, they reject the McConnell approach solely on the basis of policy. Only about 20 percent of the Wall Street Journal/NBC respondents think cutting Medicare or Social Security will “significantly reduce” the deficit.

They’re right; although you wouldn’t know it from most of the coverage, those two programs have nothing, literally nothing, to do with the current deficit. There are longer-term challenges; but by itself, lifting the $107,000 ceiling for the payroll tax would make up almost the entire future shortfall in the Social Security trust fund.

Of course, Obama will be criticized by the keepers of establishment orthodoxy, especially the editorial boards, if he declines McConnell’s invitation to become the Democratic president who undoes or undermines the work of FDR, JFK, and LBJ. Democrats have a reflexive impulse to read and heed the editorials; Republicans generally don’t care. They calculate the politics — and move ahead. On this one, Obama has the additional advantage of being right on the merits — both fiscally and as a matter of economic justice. It is up to him, in the fierce urgency of coming weeks, to transform this fateful debate as Bill Clinton did in 1995.

Clinton was blessed with Gingrich; Obama now has the boon of McConnell and the Tea Party. The Republicans just can’t seem to resist the darker calls of their ideology. It’s not that they haven’t been cautioned. Almost two weeks before McConnell climbed aboard the third rail of American politics, Bill McInturff, one of the smartest of GOP pollsters, warned that the Wall Street Journal/NBC survey was “a huge flashing yellow sign for Republicans…” McConnell doesn’t know, doesn’t care, or so eagerly caters to the anti-government extremists that he’s sped straight down that roadbed.

Stay on track, Mitch. Go ahead, make our year.