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Northwestern has one IPE person who I know about (Nelson), and I know they tend to value high GRE scores above grades, so maybe give it a shot?

This is a tough question, as both schools have great behavioralists and experimentalists. If you know that you're interested in political psychology--and know that it's the key factor in your decision--then the clear choice is Minnesota. They have a bigger group of political psychologists. However, if you're not 100% married to pol. psych., I would go with Ohio State, as it's a much higher ranked program for American Politics in general (top 5 or 10). I would also consider Northwestern; they have a good pol psych/public opinion group, and Jamie Druckman, who wrote the book on experiments (literally), is there too (see Druckman et al. 2011, "Cambridge Handbook of Experimental Political Science).

I just turned down Pitt, so hopefully that will help! The program there is getting stronger every year (especially in my field--political behavior and methods), and it was a tough decision. Hope things work out for you!