Hasn't the VP carrying states myth been debunked?
It's been muddied.
But there is the arguments that veeps can help, especially if they're popular in the home state.
One boost that doesn't help Rubio is if the running mate comes from a small state. Nate Silver tried to suggest that Brian Sandoval would have helped Romney best in 2012.
http://fivethirtyeight.blogs.nytimes.com/2012/08/08/how-romneys-pick-of-a-running-mate-could-sway-the-outcome/?_r=0It is worth noting that Mitt Romney improved Republican's numbers in Wisconsin much better than in the rest of the country (reducing Obama's 13.9 point margin in the state in 2008 to a 6.94 point margin in 2012) so 2012 could have included a running mate who helped significantly.