Mitt Romney spent the week following his back-to-back defeats in Alabama and Mississippi emphasizing his economic experience while hammering Rick Santorum as an “economic lightweight”.

Republican presidential candidate, former Massachusetts Gov. Mitt Romney holds a town hall-style meeting at the Sullivan Community Center Gymnasium March 18, 2012 in Vernon Hills, IL. (Photo by Chip Somodevilla/Getty Images)

Roughly one in five Illinois Republican voters said that a candidate having the right experience was the most important trait for them in deciding who to vote for. Of that group, Romney won 59 percent of the vote as compared to 19 percent for former House Speaker Newt Gingrich and just 8 percent for Santorum.

Those results continue a pattern we’ve seen throughout the presidential primary process. Gingrich has won among “experience” voters in Mississippi, Alabama, Georgia, Oklahoma, Florida and South Carolina. Romney has won that group in Tennessee, Ohio, Massachusetts, Vermont, Arizona, Michigan, Nevada, New Hampshire and Iowa.

Santorum has not won “experience” voters in a single state. Not one. (Read that again. It’s important.)

What’s happened, at least in Illinois, is that as Gingrich has faded as a serious candidate, “experience” voters are flocking to Romney.

That movement is significant and could well be the key to Romney’s messaging as he moved forward in the race. Arguing the delegate math or even electability hasn’t closed the sale for Romney. Focusing on his experience and contrasting it with that of Santorum is working. Expect lots more of it from Romney.