It's the reason why Mack has tied his campaign so closely to Romney's, both in his stump speech and in his scheduling. Mack tore up his Saturday plans to make sure he was with Romney's running mate, Wisconsin Rep. Paul Ryan, at a rally in Panama City even though he was in the same area just two days earlier.
Earlier Saturday, Mack made a campaign stop at a Jacksonville pizza shop, where about 20 people waited to see him. In Panama City, a Panhandle City where Mack needs to run up strong numbers, he'll be in front of a couple of thousand voters at the Ryan rally.
"Anywhere we can go where we can get in front of people and make sure that when they vote for Romney/Ryan, that they vote for Mack, it's a good thing for us, so we're excited to be there with him," Mack said. "Romney's going to need another Republican senator from Florida that he can work with and count on. Nelson is not that guy."
Likewise, Mack changed his campaign plans on Sunday and Monday to make sure he could attend a Monday appearance with Romney in the Orlando area.
While Nelson has also campaigned with Obama and Vice President Joe Biden when they've appeared in Florida, he hasn't made every appearance. And he also plays down the connection his race has with the presidential race.
"People vote for their senator not because he's running around with the presidential candidate of either party," Nelson said. "They are very, very Floridian when they make up their mind about their senator."
AP writer Gary Fineout in Orlando contributed to this report.
Follow Brendan Farrington on Twitter: http://twitter.com/bsfarrington