New Delhi, Aug. 13 -- MADISON - Ali Plummer knew which candidate she agreed with. The Madison voter preferred Francesca Hong's politics, the democratic socialist's platform on healthcare, housing, and climate change that matched Plummer's own instincts. But on Tuesday, Plummer voted for David Crowley anyway, telling a reporter outside her polling place that she needed someone who could win in November.

"I wanted her policies," she said, "but I voted for who I thought could beat Tom Tiffany."

Crowley won. He won despite being listed at 7 percent in the most recent Marquette University Law School Poll, which gave Hong a 38 percent share of likely Democratic primary voters and projected a field with one-third undecided as recently as July ...