McCain is 71 and would be the oldest person ever elected to a first presidential term. He has survived a bout with melanoma that left a long scar on his face and suffered harsh treatment as a Vietnam prisoner of war.
Voters do not typically base their vote on the vice presidential choice but they do want to be assured that the running mate would be able to take over if the president were to die or become incapacitated.
When questions arose about Ronald Reagan’s age, 69, during the 1980 election, Reagan picked one of the men he had vanquished for the Republican presidential nomination, George HW Bush, and Bush’s reassuring presence largely silenced questions about Reagan.
It is a scenario not lost on the McCain team, which is waiting to seal the Republican presidential nomination before launching a search for the No 2.
“For Reagan in 1980, age was a big question, was a bigger issue than it is for McCain,” said McCain adviser Charlie Black. “The day Reagan picked George Bush, it went away. People said, ‘Oh, we know this guy, we know he can handle it’.”
By contrast, Americans were so disenchanted with Bush’s vice president, Dan Quayle, that the Bush team considered but decided against dumping Quayle from the ticket in the elder Bush’s 1992 re-election bid, which he lost.
Douglas Brinkley, a presidential historian, said McCain has a compelling history as a former Navy fighter pilot and Arizona senator.
“But at 71 years old and afflicted with cancer and a life that has brutalised his body in many ways, I think who he picks is going to be very, very important,” Brinkley said. “You’re really looking at somebody who over an eight-year period could be president.”
It does not necessarily mean McCain must pick someone far younger.
Brinkley said the mostreassuring person McCain could pick in the Republican Party would be retired General Colin Powell, a former secretary of state and defence.
Powell, 70, has said he does not want the job but Brinkley said Republican Party elders might be able to persuade him.
“Powell is someone everyone could imagine as president,” said Brinkley.
Two possibilities include Florida Governor Charlie Crist, 51, who could help McCain win the battleground state of Florida in the November election, and Minnesota Governor Tim Pawlenty, 47, who could do the same inMinnesota.
There are plenty of other names: Texas Senator Kay Bailey Hutchison, who says she does not want it; South Carolina Senator Lindsey Graham; Mississippi Governor Haley Barbour; Texas Governor Rick Perry; and former White House budgetdirector Rob Portman, a former member of the US Congress from Ohio.
Republican pollster Whit Ayres said McCain’s choice may well depend on whether Democrat Barack Obama orHillary Clinton wins the nomination.