As the still shell-shocked Democrats try to figure out what went wrong and what to do about it, Hillary Clinton’s formal announcement of her candidacy in 2015 would be a good starting point.

The beautifully produced two-minute video was replete with attractive and aspirational Americans. It presented a diversity of color, young, old, gay and lesbian couples, a single mother and immigrant entrepreneurs. The candidate, who appears in only about a third of the video, was comfortable and self-assured. Even though she warned that the deck was too often stacked against average Americans, her tone was upbeat.

It got good reviews for tone and content. The New York Times reported, misleadingly, that it included “plenty of white working-class people,” a signal that she would address these voters’ concerns in the campaign. A subsequent Times video chat was more insightful: Top political reporter Maggie Haberman noted that despite the video’s high production values “it’s not clear what her message is.” The theme, she said, seemed to be striking a balance between “things are getting better” and “things are great.”

For the economically struggling voters in Pennsylvania, Wisconsin and Michigan — the ones who determined the election — that didn’t seem reassuring. Their unease didn’t abate much over the next year and a half.

Democratic polls showed that voters were split almost evenly on the question of which candidates’ economic policies would help them the most. But even though the economy is better than four years ago, surveys showed that a wide range of voters had more confidence in President Barack Obama on this score than in Clinton this time.

My theory, based only in part on data and a few interviews, is that late-breaking voters, as the exit polls suggested, went for Donald Trump, despite their doubts about his abilities and character. Clinton wasn’t giving them much reason to believe things would change, so they decided to roll the dice — Trump probably wasn’t going to win anyway.