As this Salon article explains, Democrats in Wisconsin think that stem cell research could be the wedge issue that will help them win in November.
"In 2004, observers attributed much of President Bush's slim margin of victory to the clever use of a single wedge issue. Ballot initiatives banning gay marriage may have lured more conservative voters to the polls in 11 states, and Bush won all those states except Michigan and Oregon.
Two years later, Republicans are again using gay marriage to rouse their socially conservative base. In November six more states will vote on whether to ban same-sex unions. But in the battleground state of Wisconsin, early polling suggests that gay marriage may be losing some of its Election Day magic -- and that Democrats have found a wedge issue of their own with as much or more drawing power."