CNN: President Obama took his renewable energy push to the heartland Tuesday, trumpeting the merits of wind power during a visit to the state that launched him on the road to the White House a little over two years ago. Obama’s visit to the Siemens wind turbine blade manufacturing plant in Fort Madison, Iowa, was the latest stop in his “White House to Main Street” tour — part of the president’s pitch to middle-class workers hurt by the economic downturn. “Lately, we’ve been able to …