The electoral college over-represents small states like Alaska and Wyoming.....red states. It would be a.near impossibility for Romney to win popular and lose electoral...and if Silver says this might happen, he is obviously lacking in the math department.
I think the math for Silver’s (and my) conjecture requires only that Romney’s popular vote margins in the states he wins exceed the popular vote margins for Obama in the states he wins. I can imagine Obama squeaking out victories in Ohio, Colorado, and Wisconsin, for example, while Romney wins big in the South and most of the Midwest.