Justice Rebecca Bradley, left, and JoAnne Kloppenburg listen during a Wisconsin Supreme Court debate on March 15 at Marquette University in Milwaukee. (Greg Moore/AP)

Wisconsin's luckless Democrats, gerrymandered into a minority and unable to retire Gov. Scott Walker (R-Wis.), went into Tuesday night hoping for a breakthrough. They saw a decent chance to defeat Rebecca Bradley, a conservative justice appointed to the state Supreme Court by Walker. Her opponent, JoAnne Kloppenburg, nearly won a seat on the court in 2011, before late-counted ballots from conservative Waukesha County did her in. And Bradley took a crucially-timed hit when reporters and the advocacy group One Wisconsin Now revealed far-right newspaper columns, with impolitic fulminations about gay rights, from her college years.

Bradley won the election, a surprise to Democrats. This morning, some progressives picked a culprit: voters who cast ballots for Democratic presidential candidate Sen. Bernie Sanders (Vt.) and left the rest of their ballots blank. According to exit polling conducted by the independent group DecisionDesk and BenchMark Politics, perhaps 15 percent of Sanders voters skipped the Bradley-Kloppenburg race; just 4 percent of Hillary Clinton voters did the same.

"There was an enormous drop-off," said Brandon Finnigin of DecisionDesk. "There was a substantial number of voters in that voted for Sanders, then for nothing else."

Anger at the allegedly stingy Sanders voters has roiled the online left all day. Bradley won 1,017,233 votes; Kloppenburg won just 925,929. But 1,004,636 people voted in the Clinton-Sanders contest. While the judicial race was nonpartisan, Democrats were informed that Kloppenburg was their candidate, and Clinton used a speech in Milwaukee to endorse her.

"There is no place on any Supreme Court or any court in this country, no place at all for Rebecca Bradley's decades-long track record of dangerous rhetoric against women, survivors of sexual assault and the LGBT community," Clinton said on April 2.

To Clinton supporters, that advocacy was proof that she engaged in party-building while Sanders sat on his hands. The problem: Sanders also endorsed Kloppenburg. "I hope a large turnout on Tuesday will help elect JoAnne Kloppenburg to the Supreme Court," he said at his final Madison rally before the vote, on April 3.

Another problem, according to One Wisconsin's Scot Ross, was that both parties watched voters skip the Supreme Court race -- a heated statewide contest that anyone watching TV saw plenty of ads for. "Bradley got 83,000 fewer votes than the Republican presidential candidates," said Ross. "Kloppenburg got 80,000 fewer votes than the Democrats. Right there's your problem."

Indeed, the Wisconsin Republican primary saw the biggest turnout since 1980 -- 1,101,326 total votes. The fall-off hurt both parties; the defining setback for Democrats might have been that the election was held on primary day. In 2011, Kloppenburg rode a surge of voter anger at Walker's labor-reforms to her near-miss loss, with less than 750,000 votes. Her total on Tuesday would have been enough for a rout five years earlier.

Democrats, with no victories to show from Tuesday, are hardly taking solace in the turnout. The defeat of Kloppenburg and of a Working Families Party-backed candidate for Milwaukee County executive are creating tension with supporters of Clinton, who argue that she is investing in the Democratic Party's success -- and that Sanders, far from a revolution, has built a personal following but little else.