By Cokie Roberts and Steven V. Roberts

That’s the most intriguing question to emerge from the partisan standoff that closed the federal government for three days.

Two dozen moderates from both parties brokered a deal with two parts: Democrats voted to resume government funding, and Republicans leaders promised a floor vote on legislation protecting “Dreamers” — about 800,000 young people brought here illegally as children, who could face deportation if Congress doesn’t act.

Liberal activists were rightly skeptical of the deal. Promising to hold a vote is not the same as promising to pass a bill. And nothing the Senate does binds the House, where anti-immigrant hardliners oppose virtually any concession to the Dreamers.

Still, it is cause for hope that senators from both parties actually talked to each other, respected each other, trusted each other. So many senators wanted to join the bipartisan meetings hosted by Sen. Susan Collins, a Maine Republican, “that we were running out of chairs,” she said.

For years, Congress has been dominated by extremists on both sides who denounce any concession to the other party as betrayal — or even treason. The senators who crammed into Collins’ office were rebelling against that wrong-headed notion. And they were reasserting a basic truth: that effective legislating requires compromise — one of the noblest words in the political lexicon.

These senators have taken a step, a very small step, toward returning reason and realism to Capitol Hill. If that step leads to more conversations, and more compromises, the long-term impact could be highly significant.

As Sen. Claire McCaskill, a Missouri Democrat, noted: “There was a large group, 25 senators almost evenly divided between the parties, that immediately went to work and fixed this, and that’s the way this place is supposed to work.”

Added Sen. Dick Durbin of Illinois, the second-ranking Democrat: “What I have seen here on the floor of the Senate in the last few days is something we have not seen for years.”

There are plenty of reasons to be cautious here. In 2013, an immigration reform bill passed the Senate with strong bipartisan support, then got buried in the House without even a vote. The same fate could meet any Senate measure empowering Dreamers.

The two chambers are very different. Senators run statewide and as a result, they’re forced to listen to dissenting minorities. Republicans like Cory Gardner of Colorado and Dean Heller of Nevada have growing Latino constituencies to consider, while Democrats like Heidi Heitkamp of North Dakota have to survive in very red states. Inevitably, that makes them more responsive and flexible.

House members, by contrast, have small districts that are often tailored to protect one party. That reduces their incentive to consult the other side to almost zero. Their biggest political fear is often a primary challenge from an even more hardline rival.

Add in many other trends — ideological purists pouring money into campaigns, biased media echo chambers, voters who move to places with like-minded neighbors — and the drift toward hyper-partisanship sometimes seems unstoppable. Which is why this flicker of friendliness across party lines — “the way this place is supposed to work,” as McCaskill put it — could really matter.

But only if the moderates keep at it. Their first challenge is to agree on a truly bipartisan bill that offers significant benefits to both sides. Liberals would get citizenship for the Dreamers; conservatives would get enhanced border security, even a wall in some places, and some movement toward a more merit-based immigration system.

The red-hots on both sides will scream “sellout,” but the centrists have to stay strong. It helps that in the latest Pew poll, 74 percent of respondents favor protecting the Dreamers.

But merely passing a bill through the Senate will not be enough. Members of the “half a loaf caucus” have to attach their handiwork to a must-pass appropriations measure. And they have to convince President Trump to back their bill and sell it to House Republicans. Without his support, it’s hard to see any meaningful measure becoming law.

This statement from the Washington Post editorial board got it right: “From here, that core group of moderate, deal-making lawmakers should feel empowered. The broad middle in both houses of Congress should no longer wait for direction from a chaotic White House or spineless congressional leadership. They may discover that they have more in common with members of the other party also interested in competent, responsive government than they do with the ideologues in their own camp.”

That really would be “something we have not seen for years.”

Steve and Cokie Roberts can be contacted at stevecokie@gmail.com.