Through the tall trees of northern Wisconsin, Republican Sean Duffy is stalking a giant. The 38-year-old district attorney is talking fiscal responsibility, job creation, entitlement reform. He’s scoring Washington for higher taxes, and for a health-care takeover. He’s Facebooking and Twittering. He comes across as a serious yet positive reformer, a combo that has caught the public’s eye.

He’ll need that eye, and more, since his Goliath is one David Obey, Democratic head of the Appropriations Committee, the liberal bull who has occupied Wisconsin’s Democratic-leaning 7th congressional seat since before Mr. Duffy was . . . born. That the Republican is getting some traction says something about how bitter voters are with the Democratic agenda. It says something equally important about a nascent GOP effort to rebrand the party.

Meanwhile, in the you-can’t-please-anybody department, unions are complaining about ObamaCare:

Local unions are waging war against President Obama’s proposed “Cadillac tax” on higher-cost health-care plans — with one leader warning New York Democrats who approve the levy to watch out at the polls this year.

“The proposed tax is both terrible politics and bad policy, and it’s going to seriously undermine good health-care coverage for literally tens of millions of middle-class workers,” fumed Bob Master, legislative and political director for Communication Workers of America’s Northeast chapter.

“We are working furiously to ensure that the New York House delegation stand strong on this,” he added. “On the political side, I can tell you — and this is not a threat — that union members and middle-class voters whose taxes go up because of their health care, or whose health care gets cut, are not going to turn out for Democrats in hotly contested elections.

“I think they just stay home.”

Master pointedly mentioned the wave of anti-Democratic sentiment in upstate elections last year, as well as the New Jersey and Virginia gubernatorial races.