The only way to win is to compete. If you cede the bulk of the country to your opponent, you don't get to be president.
The polls have tightened considerably in Wisconsin because Hillary Clinton has chosen to contest it. She may still become the nominee. If she runs the general election the way she's run this primary though, we're screwed. Obama -- advantaged with a lot of cash and enthusiastic supporters -- has fought for every vote on every inch of soil all across the country.
She's got to make some miracles happen to win at this stage. Her strategy, a standard political strategy of focusing on the big states and ignoring the smaller prizes, has finally been revealed as the loser it always was. I question her wisdom and her management skills, and unless she radically turns things around and fast, I can't think of a single reason to support her quest for the nomination.