By Mark Halperin, Time.com – Smart Democratic pollster and strategist Mark Mellman is able to look at data without debilitating partisan blinders.

So read his fascinating breakdown of some recent Pew research that suggests that the polarized attitudes of the American people have in some cases been shaped by the moves and views of their party leaders.

For example, African-American support for same-sex marriage bumped up after the President came out in support of the practice.

More ominously for Mellman, Republican voters’s views on the environment and labor unions have changed dramatically, led from Washington.

Unpacking and dealing with the roots of our corrosive partisanship is going to take time and effort; Mellman’s point is a helpful step along the way.

Whether winning for you means getting more votes than your opponent, selling more product, changing public policy, raising more money or generating more activism, The Mellman Group transforms data into winning strategies.