DES MOINES, Iowa — The stop signs have been uprooted here as the top four Democrats barrel toward the intersection of Tuesday night's final debate before the Feb. 3 Iowa caucuses, and they all have their feet on the gas.

While six candidates will clash at Drake University, the competition for first is among the four contenders — former Vice President Joe Biden, Sen. Bernie Sanders, I-Vt., former South Bend Mayor Pete Buttigieg and Sen. Elizabeth Warren, D-Mass. — who are bunched up from 16 percent to 20.7 percent in the Real Clear Politics average of recent polls.

In recent weeks, they have stepped up their attacks on one another — drawing "contrasts" in the euphemistic language favored by political pros — as they compete over the scarce resource of caucusgoers. Leaders of the progressive set are hoping Sanders and Warren put aside their differences Tuesday long enough to gang up on Biden, who has been largely untouched in the fracas.

Here's what to watch as the front-runners are joined on stage by Sen. Amy Klobuchar of Minnesota, who has struggled to make the leap into the top group, and billionaire Tom Steyer, who has seen his poll numbers in states that follow Iowa rise along with the expenditure of more than $100 million.

1) The War Within the War — Before Monday, it looked like one of the main lines of discussion would be who was the candidate of the elite. Warren has pointed at Buttigieg, and, more recently, Sanders' supporters have tried to differentiate their candidate from Warren by casting her in that light.

The underlying point of that attack is the same as the rest of the hits on her — from Buttigieg, Biden and others — that she is less honest than her rivals. Warren backers see that whole line of reasoning as sexist, given that each of her opponents has shifted positions on policies, and she unloaded on Sanders Tuesday by confirming a report that he had told her in a 2018 meeting that a woman couldn't win the presidency.

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Now Democratic candidates are far more likely to be asked to answer that question — and surely, they will all say yes — rather than whether Warren is an elitist. Or, at the very least from Warren's point of view, they'll be asked both questions. Don't be surprised if Sanders notes the campaigning he did for Hillary Clinton in 2016 or the support he has from three young women lawmakers: Reps. Alexandria Ocasio-Cortez, D-N.Y., Rashida Tlaib, D-Mich., and Ilhan Omar, D-Minn.

2) Praying for De-escalation and Re-concentration — The carefully laid plans of the progressive movement — running a one-two punch of Sanders and Warren or Warren and Sanders — could be unraveling at exactly the wrong moment. Folks on the left who have spent years trying to figure out how to defeat the party establishment are praying that Warren and Sanders pivot together and remember that Biden is their target.

"I would expect de-escalation and a joint final focus on why Biden is the least electable candidate," said Adam Green, co-founder of the Progressive Change Campaign Committee, which has endorsed Warren but has also praised Sanders.

But Sanders can be easily agitated in stressful moments, and his ability to stay focused on Biden could help determine the fates of all three candidates in Iowa.

3) The Actual War Debate — President Donald Trump's decision to kill Iranian Gen. Qassem Soleimani has sparked a renewed debate within Democratic circles about the war powers granted to the president through the authorization for the use of military force in 2001 and 2002.

Sanders has been one of the most vocal critics of the U.S. prosecution of the wars in Afghanistan and Iraq, and he was the only leading Democrat to ignore Soleimani in his first statement after the strike and jump right to warning about the possibility that Trump might use his authority to go to war with Iran. He has lashed Biden over his vote for the 2002 authorization of military force that led to the Iraq War.

But Sanders voted for the 2001 authorization, which a president might use as justification for military action against Iran, and he called for regime change in Iraq before the Sept. 11, 2001, terrorist attacks on the United States and President George W. Bush's push to connect them with Iraqi leader Saddam Hussein. He could be open to counterattack on his unwillingness to forgive Biden and others for what Biden calls a mistake in judgment on the Iraq War vote when Sanders forgives himself for a "wrong" vote on Afghanistan and doesn't talk about his one-time support for overthrowing Hussein.

4) A Third Way? — Buttigieg is the only one of the candidates to have worn a military uniform, and while the Iran tension presented a perilous moment for him in terms of lack of experience in national politics it might also give him an opportunity to talk about the issue in a forward-looking way that reflects the glimpses he's shown that he shares the war weariness of his generation.

That is, he could leave the last generation debating the wars they started — one of which he served in — while he offers a means of making sure mistakes of the past aren't repeated in the future.

5) Klobuchar's Choice — Klobuchar has been one of the most capable debaters throughout the first year of the campaign, which has kept her afloat despite a lower profile and smaller fundraising numbers than her competitors. But she may have to decide in this debate whether she goes for broke and tries to score a top-four finish in Iowa or perhaps aligns herself as a wing-person for one of the other candidates on the stage. It's worth watching who she goes after and how to determine what her plans are for the final weeks before the caucuses.