For anyone who has paid only scant attention to the Democratic nomination contest, it took only a few minutes yesterday to grasp the state of the race.
Two weeks before Iowans gather for their caucuses, Hillary Clinton sought to blunt the momentum behind Bernie Sanders' grassroots insurgency.
In response, Sanders raised the volume and the stakes, appealing to Democrats to support his call for a political revolution.
For two hours, the leading candidates for the nomination traded arguments over guns, healthcare, Wall St, taxes and political change.
But at heart, those issues were fodder for a display of competing styles, ambitions and arguments about how much to embrace the policies and record of the Obama Administration and build on them.
At moments, role reversal seemed to be under way. Clinton, still considered the favourite to win the party's nod, aggressively challenged the details of Sanders' agenda as if her nomination was at risk.
Sanders, the underdog who has energised the grassroots, sought to keep focused on the big picture and a clarion call for change in what appeared to be an effort to prevent any erosion in his strength and standing.
There were good reasons for Clinton's posture in the debate. With polls showing a tightening race in Iowa, she cannot afford a loss there on February 1. So she set about trying to raise doubts about where Sanders stands and whether he can really do what he says he wants to do.
The differences between the two were most apparent in a very sharp exchange over healthcare - a dramatic argument over the best way to insure the most Americans and a proxy for who has a governing strategy that can produce results.
Sanders has called for a "Medicare-for-all" programme, a single-payer system, to replace the Affordable Care Act enacted during Barack Obama's presidency. Clinton warned that what Sanders has proposed amounts to starting over and threatens to plunge the country into a new and highly contentious fight just as the ACA is taking hold.
Rarely have Clinton and Sanders so underscored their contrasting views of the presidency. Clinton has become the candidate of continuity. She has differences with Obama on some issues, particularly in foreign policy.
But in these final days before the first votes are cast, she has emphasised time and again her desire to extend and build on what the President has done in domestic policy.
Sanders wants to go much further, and he has found an audience inside a Democratic Party whose liberal wing shares his critique of the political system as dominated by the rich and the elites and applauds him for wanting to use the power of big government to raise wages, rebuild the country's infrastructure and break up the big banks.
The debate reflected the campaign in another way. There was a sense of urgency in the performances. They talked over and past one another.
It's not likely the debate changed many minds, but it might have reinforced the supporters each of the candidates has. There are undecided voters in Iowa and New Hampshire, and history suggests that minds will change between now and those contests. But it will be left to Clinton and Sanders barnstorming over the next weeks to drive those voters in one direction or another.
- Washington Post, Bloomberg