As usual, a lot of mixed economic news recently. The automobile industry is booming, and so are parts of the farm economy. Both are major pluses for Obama. The “Morning Joe” show on MSNBC had a great segment with Agriculture Secretary Tom Vilsack, who I doubt gets a lot of mainstream airtime. That’s a shame, because he has a great story to tell about farm exports really helping to boost the economy in some states.

A USA Today poll shows that Americans are more optimistic the economy will improve, which should help Obama, but respondents believe the economy will do better under Romney.

I have a theory I’ve floated before about the election, which is pretty simple. If the unemployment rate is 8.4 percent or higher, Romney will win relatively easily. If it is below 7.9 percent, Obama will win. But if it is somewhere in the middle of those two points, the race will be historically close and the skill of the candidates and campaigns will be determinative.

Now let’s apply that theory to the battleground states. I chose to use the list on Real Clear Politics, but there are others. Here is a list of the RCP battleground states, matched with their March unemployment numbers.

Arizona 8.6%

Colorado 7.8%

Florida 9.0%

Iowa 5.2%

Missouri 7.4%

New Hampshire 5.2%

North Carolina 9.7%

Ohio 7.5%

Virginia 5.6%

So according to the theory, Obama wins Colorado, Iowa, Missouri, New Hampshire, Ohio and Virginia. Romney picks up Arizona, Florida and North Carolina.

Distributing these results to the RCP electoral map model results in a victory for Obama, with 313 electoral votes to Romney’s 225.

Of course, there are many flaws to this analysis, chiefly that it doesn’t account for the impact that national unemployment numbers have on the psychology of all Americans, regardless of how well their particular state may be doing. But presidential elections are increasingly a series of state-wide elections; that’s where the real battle is fought. So it will be interesting to see whether Obama can use an economic success argument more successfully state-by-state, instead of nationally.