Scott Walker has yet to launch his presidential campaign, but the Wisconsin governor is already talking both privately and publicly about a running mate: Marco Rubio.

This comes as news to Rubio, the freshman Florida senator who is running his own campaign to be president. The constant prodding from Walker has become an irritant between the two GOP rivals, neither of whom knows the other all that well.

The goal for Walker is clear: to calm the nerves of Republican power brokers who love his conservative message and anti-union pedigree but who worry about the appeal of a white male Midwestern governor in a fast-changing country — especially if Hillary Rodham Clinton is the Democratic nominee.

It also less-than-subtly suggests that one of his rivals is not up for the top of the ticket.