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One of Wisconsin Gov. Scott Walker's strongest selling points in his White House bid is that he won his state – a presidential battleground – three times in four years.

But what happens when he longer looks as strong in Wisconsin?

A new Marquette University Law poll – considered the gold standard in Wisconsin – shows that Walker's job-approval rating in the state has sunk to 41 percent among registered voters. That's down from 49 percent in October before his successful re-election.

The poll also shows Walker trailing Hillary Clinton in the battleground state by 12 points in a hypothetical general-election match up, 52 percent to 40 percent.

And in a possible 2016 Senate rematch, the poll finds Republican Sen. Ron Johnson trailing 2010 Dem opponent Russ Feingold by a whopping 16 points, 54 percent to 38 percent.

The poll was conducted April 7-10 of 803 registered voters in Wisconsin, and it has a margin of error of plus-minus 3.5 percentage points.