John McCain represents the last chance for a Vietnam Veteran to be elected President. Every other war has had one or more veterans become president. The usual pattern was set with our first President, where the over-all commanding General succeeds to the Presidency, this seems to be especially true for our big wars -- Grant from the Civil War and Eisenhower from WWII. The war of 1812 gave us Andrew Jackson and the First Harrison. The Mexican American war gave us Zachary Taylor and Spanish American War gave us its one hero -- Teddy Roosevelt. WWI gave Truman as its vet that served (that's counting Ike as a WWI vet, although he was also WWI) Both the Civil War and the Second World War were long tail conflicts as far as vets becoming President -- from Grant to McKinley we were electing Civil War Vets and WWII vets were getting in until 1992 when Bush the first finished up his term.
Korea may or may not be an exception -- Carter was a Korean War era vet, but studying nuclear subs did not see action.
So McCain is the last hope for the Vietnam vets.