Yes, Oklahoma is a very red state. But when Democrats reject their own party leader in this fashion, it opens a door for the GOP nominee to try to appeal to these dissatisfied voters.

ABC:

Veteran anti-abortion activist Randall Terry won more than 18,400 votes, or 18 percent, in Oklahoma's Democratic presidential primary Tuesday - a not insignificant showing in a year when incumbent President Barack Obama has nationally faced no serious challenge from within his party.

Obama won more than 54,000 votes, or 55 percent, according to preliminary results from the Oklahoma State Election Board. Democrats who turned out did so largely in a symbolic show of force for Obama in one of the nation's reddest states. (Republican Sen. John McCain carried Oklahoma with 65 percent of the vote in 2008 to Obama's 34 percent.)

Support for Terry highlights, at least in part, the prevalence of anti-abortion Democrats in the country's mid-section, where social issues are of comparatively higher salience for all voters.

AP reports that Terry won 12 counties in Oklahoma and is eligible for one delegate.

These are largely working class Democrats who may be a little more centrist or populist on economic issues, but are conservative values voters. Santorum has shown that he can attract these voters in Michigan, Ohio, and some other states while Romney can't.

Can Romney alter his general election message to appeal to these voters? He probably won't win unless he does.