WASHINGTON -

Mitt Romney's campaign says the presumed Republican presidential nominee will announce his running mate Saturday morning in Norfolk, Va.

The short list -- if there is one -- is believed to include Ohio Rep. Rob Portman, former Minnesota Gov. Tim Pawlenty and Wisconsin Rep. Paul Ryan.

In a statement issued Friday night, the Romney campaign said the running mate would be revealed at 9 a.m. EDT at the Nauticus Museum. Romney is kicking off a four-day bus tour through swing states.

Romney's choice comes as he tries to repair an image damaged by negative Democratic advertising and shift the trajectory of a campaign that's seen him lose ground to President Barack Obama.

The vice presidential selection will dominate headlines, and Romney's team has been relentlessly teasing the announcement for weeks.