Pollsters missed again in Wisconsin. Here's why.

Pollsters appeared to blow another high-stakes Midwest election Tuesday, as center-left Democrat David Crowley stunned socialist Francesca Hong in Wisconsin's primary for governor.

But on Wednesday, the reasons for the miss seemed clear: Surveys a week before the primary captured only a hint of a rapidly changing roller coaster of a race in which Crowley was gaining fast, and Hong was playing defense.

Driving the news: Two polls had shown Hong up by about 20 points over Crowley.

But Crowley wound up winning by half a percentage point in an upset that interrupted a run of primary wins by left-wing Democrats this spring.

Just a week earlier, polls also had overestimated progressive Abdul El-Sayed's strength in the Michigan Senate race by double digits.

He won by 1 point.

Polls help shape the pre-election narrative for campaigns, but the Midwest misses were reminders of the surveys' limitations in capturing voters' feelings over just a few days in a long race.

In the days before the primary, even Crowley's own pollster had him down by nearly 20 points.

Zoom in: The final month of the gubernatorial primary was particularly chaotic.

There was a mad dash by the party's establishment to stop Hong out of fear that the state Assembly member was too far left to win in November.

Two candidates dropped out amid sudden scandals.

Crowley, the county executive in Milwaukee, actually exited his campaign as well — then re-entered the race to try to take out Hong.

The last week of the campaign was dominated by the fallout from Hong struggling to explain to CNN why she'd once taken to social media to say "cancel Thanksgiving." Amid that hurricane , Democratic strategists saw late-deciding voters flocking toward Crowley as he barnstormed Wisconsin with Democratic Gov.

Tony Evers, questioning Hong's electability.