Tesla Motors has five states bidding to attract a $5 billion factory that will make batteries for a new generation of electric cars. The winner is expected to offer publicly financed incentives exceeding a half-billion dollars.

And the package could be far more, because the states don't know what their competitors are offering.

So far, Tesla has done initial work on a potential site in Nevada. But the company will prepare at least one other before making a final decision by year's end.

That leaves California, Texas, Arizona and New Mexico wondering what they can do to be a finalist.