AFL-CIO President Richard Trumka: "Candidates can't hedge their bets any longer, and expect workers to rush to the polls in excitement." Alex Wong/Getty Images hide caption

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Gov. Scott Walker arrives at the First in the Nation Republican Leadership Summit in New Hampshire. Walker has long been a polarizing figure due to his epic battles with public employee unions, but a new poll this week shows a new and sizable drop in his approval rating. Darren McCollester/Getty Images hide caption

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At this stage in the election cycle, just like in baseball's spring training, fans love to see a new phenom catch fire. Wisconsin Gov. Scott Walker, sporting a Milwaukee Brewers jersey in 2013, seems to be the rookie to watch in the 2016 presidential race so far. Manuel Balce Ceneta/AP hide caption

itoggle caption Manuel Balce Ceneta/AP

Barack Obama as a presidential candidate in Selma, Ala., in 2007 re-creating a voting rights march that was violently repressed by state troopers in 1965. Roberto Schmidt/AFP/Getty Images hide caption

itoggle caption Roberto Schmidt/AFP/Getty Images