Republican pollster Frank Luntz started the night of the first presidential debate with a group of undecided Pennsylvania voters who were favorably inclined toward Donald Trump. He finished it with a group that thought Hillary Clinton had overwhelmingly won.

It’s important not to draw broad conclusions from such a small group. (A CNN focus group of Florida voters came to a similar conclusion.) But Luntz’s Twitter timeline is still an interesting illustration of where Clinton broke through and how Trump didn’t.

During the first half-hour of the debate, Luntz’s focus group broke strongly for Trump. But as the night continued, his support fell apart, particularly at a few key moments — when Clinton criticized Trump for not releasing his tax returns and when he struggled to explain being a birther.

When Clinton called out Trump for not releasing his tax returns, and speculated about several reasons he might be avoiding it, including that he’s not as rich as he claims to be, even Trump voters liked it:

Even Trump-leaners agree with Hillary. They want to see his taxes. #DebateNight pic.twitter.com/HJv2s2yTnf — Frank Luntz (@FrankLuntz) September 27, 2016

When Clinton accused Trump of stiffing contractors who worked for him, because Trump claimed they didn’t do the work up to his standards, her criticisms were more effective than his rebuttals.

Hillary Clinton has learned how to bait Trump. He doesn't know how to not take it.



Her attacks work. His defenses don't. pic.twitter.com/6GktBxBwiq — Frank Luntz (@FrankLuntz) September 27, 2016

Clinton’s reflections on race, and particularly her promise to enforce the law the right way, got rave reviews from Luntz’s focus group:

Voters across the aisle agree with the racial problems that Hillary laid out, and what must be done to fix them. #DebateNight pic.twitter.com/sJHfNNnhsX — Frank Luntz (@FrankLuntz) September 27, 2016

But Trump’s response on his birtherism appears to be what really destroyed him with Luntz’s focus group.

Trump is tanking when trying to explain why he questioned Obama's birthplace for so long.#DebateNight pic.twitter.com/WRXVShI1AC — Frank Luntz (@FrankLuntz) September 27, 2016

Hillary's response to the birther issue scored better with Trump-leaners than Donald Trump's answer to the birther issue.#DebateNight pic.twitter.com/hB5FMnbChq — Frank Luntz (@FrankLuntz) September 27, 2016

One interesting thing about these focus groups is that in some cases, voters leaning toward Trump had a better opinion of Clinton than the “undecided” voters did. Luntz’s tweets before the debate suggested that some of his “undecided” voters weren’t necessarily hovering between the two candidates with no opinion — they just didn’t like either of them. But it appears they disliked Clinton ever so slightly less.