When it came to the actual details of governing, Senator Russ Feingold, a Democrat of Wisconsin, trounced his Republican challenger, Ron Johnson, in a debate in Wausau, Wis., on Monday night. He knew that the new health care law will not reduce Medicare spending but will slow its staggering rate of growth. He knew that a vast majority of small businesses would not pay higher taxes if rates went up on the wealthy and that global warming isn’t caused by sunspots. He knew that without the 2009 stimulus there would be at least 1.5 million fewer people with jobs.

Mr. Johnson, on the other hand, proudly proclaimed recently that he doesn’t “think this election is about details.” That’s as good an explanation as any of why  in Wisconsin as in so many states  candidates like Mr. Johnson are ahead in the polls. Insurgent Republicans don’t need details when they can play on the furious emotions of voters who have been misled into believing that positive changes like the health care law are catastrophic failures.

The public’s lack of attention to detail, and Mr. Johnson’s willingness to exploit it, could end the career of Mr. Feingold, who in three terms has distinguished himself for trying to bring fairness to campaign finance and decency to national security, among other achievements. He has routinely crossed party lines to work with Republicans and has had the courage to break with his own party more often than almost any other senator.

He voted against confirming Tim Geithner as Treasury secretary, citing Mr. Geithner’s personal tax issues. He refused to support the Wall Street reform package because it did not go far enough. He was the only senator who voted against the misguided Patriot Act in 2001. He has supported gun rights  more than we like  and has opposed hate crime measures.