How resounding was Kamala Harris’s debate win? Let’s look at the polls.

Vice President Kamala Harris turned in one of the more resounding debate performances in recent decades on Tuesday night — to the point where Donald Trump’s allies have struggled to locate a silver lining.

Precisely how much the debate could impact the race is an open question, as my colleague Dan Balz notes; we’re a very polarized country, and we don’t generally see big and sudden shifts in polls anymore. But small margins can matter greatly in our increasingly tight elections, and Harris clearly helped her cause.

So just how emphatic was her win? And what do the polls suggest about what it could mean moving forward?

We’ve so far seen two instant polls — one from CNN and another from YouGov.

The CNN poll showed Harris winning the debate 63 percent to 37 percent among debate-watchers, while the YouGov poll showed her winning 54-31 among registered voters who watched at least some of the debate, with 14 percent unsure. (Trump has cited his own improbably wide margins in some unscientific online polls — posting a series of them on Truth Social — but those polls don’t reflect the actual electorate.)

Notably, those margins are close to the ones Trump racked up after President Joe Biden’s disastrous debate performance on June 27, a performance that ultimately led him to drop out of the 2024 race. Back then, the CNN poll showed Trump winning the debate 67-33, while the YouGov poll showed Trump winning 43-22.

Harris’s performance also ranks up there with the more decisive wins in recent history, according to CNN’s numbers, though it’s worth noting that a strong debate doesn’t always necessarily translate into a White House victory.

The biggest margins:

• Biden’s 60-28 win in his first 2020 debate against Trump, when Trump was widely panned for constantly interrupting and strained to avoid repudiating white supremacists.
• Hillary Clinton’s 62-27 win over Trump in the first debate of 2016.
• Mitt Romney’s 67-25 win over then-President Barack Obama in the first debate of 2012.
• Then-President Bill Clinton’s 59-29 win over Bob Dole in mid-October 1996.

Harris’s margin was bigger than 20 other polls CNN has conducted after debates, dating back to 1984. Harris was also deemed the winner of the debate by 31 percent of Trump supporters — similar to the 30 percent of Biden supporters who said Trump won the June 27 debate.

As for how much the debate could actually shift votes, the evidence is mixed but mostly encouraging for Harris.

Perhaps the worst numbers for Harris in the poll were on issues. Despite her win, debate-watchers still preferred Trump by 20 points on the economy (55-35) and 23 points on immigration (56-33). Those are actually bigger margins than he usually racks up on these issues, so it seems possible Trump’s attacks on the Biden administration’s record on these issues landed with some effect. (We’ll await more polling on these issues.)

But the data suggests voters could re-examine the race in a way that could benefit Harris.

The finding that really jumps out at me: While few voters said the debate changed or could impact their vote, Trump voters were about twice as likely as Harris supporters to say it at least made them “reconsider” it.

Nearly one-quarter of Trump supporters said that; 6 percent said it changed their vote, and 17 percent said it made them reconsider it. That’s more than the Biden supporters who said the same after the June 27 debate. And if Trump loses even a fraction of those voters, that could matter.

Trump also seemed to suffer from his often-gauzy plans. Despite some consternation about a lack of a detailed policy agenda from Harris, debate-watchers said Harris provided “a better plan for solving the country’s problems” by a 42-33 margin. That’s a reversal from the first debate, when voters thought Trump had a better plan than Biden by a 15-point margin.

Favorable opinions of Harris also increased by six points among debate-watchers, from 39 percent before the debate to 45 percent. That’s the biggest image gain for a candidate in the seven times CNN has asked this question before and after a presidential debate since 2008.

But it’s not actually the biggest shift in all CNN debate polling. The pollster asked the same question before and after the 2020 vice-presidential debate, when Harris faced then-Vice President Mike Pence. Harris not only won the debate 59-38, but her favorable ratings also increased by seven points among debate-watchers.

And that gets at a reality that many people perhaps didn’t appreciate ahead of Tuesday night: Harris is a good debater. Despite being an unpopular vice president whose 2020 Democratic presidential primary campaign flamed out before any votes were cast, she’s often done well in these settings.

Polls of early 2019 debates showed Harris was deemed the winner in a crowded field by 30 points, 28 points and 15 points. Another poll in Iowa around that time showed half of voters were impressed with her performances — more than 20 points higher than for any other candidate.

Harris wasn’t able to capitalize on that as the 2020 primary season wore on. But this big debate win comes at a more crucial juncture in the campaign. We’ll see how it impacts the race in the coming days — as we get better data than instant polls can provide — but it’s pretty evident it’s a net positive for her.