(CNN) -- It's one of the largest age gaps between presidential candidates in American history.
John McCain and Barack Obama
Only 20 percent of those polled said Sen. John McCain's age would be a factor when they voted in November.
Republican Sen. John McCain is 72, a skin cancer survivor, and would be the oldest man sworn in for a first term as president. His opponent, Democratic Sen. Barack Obama, is 47 and the fourth-youngest major party nominee.
A new CNN/Opinion Research Corp. Poll finds that may be a political liability for McCain. Nearly half of the Americans surveyed, 47 percent, are concerned that McCain would not finish a four-year term as president in good health.
To pre-empt those concerns, McCain has allowed reporters -- including CNN chief medical correspondent Dr. Sanjay Gupta -- to look through more than 1,100 pages of his medical records. This spring, McCain's personal physician, Dr. John Eckstein, released a letter saying there is no medical reason "that would preclude McCain from fulfilling all the duties and obligations of the president of the United States."