Here is what we learned about the 2020 Democratic primary from the debates Tuesday and Wednesday nights.

The race is fluid

Former Vice President Joe Biden may be the nominal leader, but he is a weak one at this stage. After two rounds of debates, and with at least four candidates in strong contention for the nomination, the race is anyone’s to win. While Biden’s polling numbers remain strong nationally, he has slipped in some early states against competitors who got into the race earlier and have more staff on the ground.

Allies had hoped that Biden, 76, would use the debate Wednesday to reassert his dominance and assuage worries from voters that he was too old, too old-fashioned and too moderate. But his performance instead continued to raise questions about whether he can articulate his vision for the country — and whether the country wants to hear it.

Since entering the race, Biden’s pitch to voters has been that he is the safe pick — politically moderate, rhetorically traditional and, above all, best positioned to beat President Donald Trump. Though his performance Wednesday was better than his one in June — he delivered pointed critiques of some challengers, defended his record and appeared more energetic and prepared — he has failed to claim control, neither proving his ability to deflect attacks nor to land his own blows.

A night earlier, Sens. Bernie Sanders and Elizabeth Warren — the two liberal populists arguing for big, structural change — turned in especially strong debate performances, articulating policy proposals and cleanly attacking the type of within-the-system ideas Biden espouses in a way that gained plaudits from supporters and detractors alike.

Sen. Kamala Harris, the candidate who benefited most from her strong performance in the June debate, was less effective in attacking Biden this time, but nevertheless proved herself a tenacious fighter.

And Sen. Cory Booker, who has been stuck in the middle of the 2020 pack, made a case for himself, too, punching at Biden for invoking President Barack Obama only “when it’s convenient” and continuing to hammer him on his criminal justice record.

Sanders and Warren had the sharpest messages

The race’s two leading progressives, Sanders and Warren, dominated Tuesday night’s debate by defending their uncompromising vision against more moderate ideas. Over and over, as centrist candidates argued that Sanders and Warren’s policies were impractical, they made their case that Trump was not the root of America’s ills, and advocated, as Ms Warren calls it, “big, structural change.”

They were helped by two factors. They had significantly more name recognition — and support in the polls — than the people who were attacking them, including former Rep. John Delaney of Maryland and former Gov. John Hickenlooper of Colorado. With them as a foil, Sanders and Warren were able to more easily remain above the fray. However, there is also an ease in defending the progressive vision, because it is aspirational. While other candidates are forced to argue about political possibilities and moderation, the two senators can think bigger and bolder, and ask the audience to do the same.

The hard question for both, which they have avoided on the debate stage to this point, involves how they would pass their policies in a polarized Washington. And many Democrats remain worried that a message of radical change could be perilous in a general election, noting that moderates had a strong track record in the 2018 midterms and that Obama and President Bill Clinton came from the center of the party.

It’s time for all the front-runners to debate each other

Biden and Warren represent two drastically different paths forward for the Democratic Party in 2020.

But so far, they are the only top-tier candidates that have yet to debate each other, and their eventual matchup could be one of the most illuminating to date about the future of the party.

Biden favors thematic messages about American unity and anecdotes about his time in government over drilling down into policy prescriptions. As he demonstrated repeatedly Wednesday night, he is running as an unabashed center-left Democrat. Biden is betting that the Democratic electorate is more moderate than the party’s loudest voices would suggest, and that his message would have broad appeal in a general election.

Warren revels in wonkery and is capable of pressing Biden on the details he sometimes glosses over. She is calling for far-reaching structural reform to address inequality in America and is seeking to expand the electorate rather than focusing on the centrist swing voters to whom Biden is trying to appeal.

Lower-tier candidates tried to shine — with mixed success

Since the Democratic debate in September raises the threshold for entry, Democratic candidates outside of the top tier knew that July was possibly their final moment to make an impression to the national audience.

With that in mind, most were more vocal in calling out the race’s front-runners than in the June debate, and some made the case directly to the audience: you want my voice on the next debate stage.

Rep. Tulsi Gabbard of Hawaii took direct aim at Harris, saying her record as a prosecutor in California hurt minority communities. Sen. Kirsten Gillibrand of New York cited a decades-old article written by Biden, which she argued espoused sexist views. Delaney tried to present himself as the moderate standard-bearer, at odds with the race’s two progressives. At times, New York Mayor Bill de Blasio sounded more like a moderator pressuring Biden to answer certain questions than a fellow debater.

But there was no breakout star among them. None landed a blow so illuminating or devastating that it dominated the post-debate analysis.

The middling result is bad news for campaigns that are desperate for a bounce. Without momentum, roughly half of the current candidates may not make the September debate stage, and some could drop out of the race before the end of the summer.

One thing to watch: The candidates currently serving in Congress — or contemplating running. Unlike those who are free to think about their future without complication, some will soon have an eye toward getting re-elected and protecting their seat. Others may start to see the merits of running for Senate instead of president.

Moderates are playing offense

While several candidates have embraced liberal policies on issues from health care to immigration to combating climate change, the moderate candidates made themselves heard more this week than at the June debates.

Of the leading Democratic hopefuls, Biden was the most vocal in espousing more centrist views on issues like health care and immigration. But he was joined Wednesday by Sen. Michael Bennet, who also landed some strong lines as he cast Medicare for All, a sweeping proposal that under Sanders’ plan would eliminate private health insurance, as too extreme.

A night earlier, a spate of low-polling moderate contenders, from Gov. Steve Bullock of Montana to Sen. Amy Klobuchar of Minnesota to Delaney, sought to cast their more progressive rivals as unrealistic and excessively far-reaching.

Those contenders face exceedingly steep uphill climbs in this crowded and expensive race, but their arguments were a reminder of the ideological diversity in the Democratic Party, and more broadly of the uncertainty about what the Democratic electorate is looking for in this campaign.

Some issues got a lot of airtime. Others got short shrift.

From the first question on Tuesday night, health care took center stage in the debates. Nearly everyone agreed that the current system wasn’t working, but there was little consensus on how to fix it. Should it be replaced with a Medicare for All plan, as Sanders and Warren argue? Or should the country take a more middle-of-the-road approach? It is a fundamental debate that is splitting the party, and it was treated during the debates as such.

Immigration, climate change and trade also got some time in the sun, affording candidates opportunities to further underscore their differences. During one exchange, for instance, after Biden rejected the idea that illegal border crossings should be decriminalized, Julián Castro, the former Housing secretary and mayor of San Antonio, suggested that Biden lacked “guts.”

But other issues frequently mentioned by voters and candidates got far less attention.

Though numerous states have recently passed restrictive anti-abortion laws, women’s reproductive rights were hardly mentioned, except for an exchange between Biden and Harris over his past support of the Hyde Amendment. Other topical issues that largely fell by the wayside included Israel, gun control and voter suppression.

This article originally appeared in The New York Times.