For anyone who has paid only scant attention to the Democratic nomination contest, it took only a few minutes Sunday night 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’s grass-roots 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 two leading candidates for the nomination traded arguments over guns, health care, Wall Street, 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 underway. Clinton, still considered the favorite to win the party’s nod, aggressively challenged the details of Sanders’s agenda as if her nomination was at risk. Sanders, the underdog who has energized the grass roots, 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 Feb. 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 health care — 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” program, 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 emphasized 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 Sanders’s critique of the political system as dominated by the rich and the elites and applauds Sanders 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 of both Clinton and Sanders. They talked over one another and past one another. Former Maryland governor Martin O’Malley repeatedly tried to interrupt, but neither Sanders nor Clinton seemed willing to yield much space to him.

In the end, it’s not likely the debate changed many minds, but it might have reinforced the supporters each of the candidates has. For sure, 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 few weeks to drive those voters in one direction or another.

With no more debates before Iowa and New Hampshire, the campaigns will be focused more than ever on final efforts to sway undecided voters and make sure identified supporters show up to vote.

The calendar ahead offers opportunities and dangers for both Clinton and Sanders. But there is no disputing that Iowa will play a huge role in establishing the tone and direction of the Democratic contest. The most recent round of polls shows the state closer than it was a few months ago, a virtual dead heat.

Iowa was the state that launched Obama toward the White House in 2008 and it is best remembered inside Clinton headquarters as the state that dealt her the cruelest defeat of the campaign. Swamped by an unexpected surge in turnout, she finished third.

This time, her organization has been built on top of those sour memories, strategically designed to maximize opportunities to win the delegate count on caucus night. But Sanders has countered with the kind of grass-roots enthusiasm that has proved successful in some past caucuses.

A Sanders victory in Iowa would boost his chances of winning New Hampshire — possibly decisively. He already holds an advantage, in part because he represents neighboring Vermont in the Senate.

Sanders victories in the first two states would dramatically change the dynamic of the race and likely guarantee a longer battle than otherwise might be expected. It would also bring about a fresh round of second-guessing among Clinton’s outside advisers, donors and loyalists.

Clinton’s team continues to feel confident about the two states that follow — Nevada and South Carolina. Her advisers see both as likely firewalls to give her a chance to regroup should she lose in Iowa and New Hampshire.

In South Carolina, Clinton’s ties to the African American community give her a potentially significant advantage. Sanders is working hard to make himself better known and more appealing to black voters.

Based on current polling, which shows Clinton with the overwhelming support of African Americans, Sanders faces an uphill struggle to make South Carolina competitive. However, his advisers, and some Democrats in the state, believe that victories in Iowa and New Hampshire would give him the opportunity to make the race here far closer.

In Nevada, Clinton won the popular vote in the caucuses eight years ago but not the delegate count. This time, she benefits from the fact that Robby Mook, her campaign manager, and Marlon Marshall, who is overseeing the first four states, were top Clinton organizers there four years ago and have been paying close attention for months to organizing efforts.

Once past the first four states, the Super Tuesday calendar sets up well for Clinton, with a group of contests in the South, where African Americans will make up a significant portion of the electorates.

But that is all well into the future. Right now, the focus is on Iowa and New Hampshire and the strength of the Clinton and Sanders ground operations. Sunday’s debate amounted to the opening of a closing argument. With the choice clearer than it has been in this campaign, Democrats are heading for a noisy and consequential showdown.