The two-time presidential candidate said as much during a GOP fundraiser at the Union League Club in Chicago, Friday afternoon.
"He just has to work hard," McCain said about Kirk's strategy to beat Democratic rival Alexi Giannoulias in November. "His military experience will give him the edge."
The Maverick senator, who's facing his own senate battle in Arizona, also thinks Kirk's jobs message will resonate with Illinois voters.
Kirk thinks so too.
"My campaign is number one about the economy," he said before entering the closed meeting.
The two have had time to talk about the campaign before their meeting today. Kirk attended a strategy session at McCain's office shortly after Scott Brown won the Massachusetts senate seat.
McCain was cautious about comparing Kirk to Brown.
"Well I think Scott Brown is certainly an incredible electoral feat," McCain said in Chicago Friday. "But you don't want to overlearn lessons from other states, Illinois is unique, I wouldn't put too much into it."
"That's right, every race is unique, my job is to earn the support of Illinois and take nothing for granted," he said.