As Jason notes below, John McCain's biographical speech was a good imitation of Bob Dole, circa 1996. Additionally, it's worth noting the speech echoed the carefully constructed biographical narrative of another recent GOP candidate: George W. Bush.
The theme of the callow young man achieving maturity and then complete identification with his patrimony is as old as the Biblical story of the Prodigal Son. It's complicated in McCain's case by the fact that his callowness, by his own account, appears to have survived the Hanoi Hilton and persisted well into late-middle-age and into his political career (viz. the admitted serial carousing, not to mention the Keating Five).
In the 2000 election, Bush's emphasized his transformation from a reckless youth with a drinking problem to a born-again Christian. That papered over his substantial negatives-- a DUI arrest and a reputation for being a spoiled brat among them--and transformed them into net positives, establishing Bush's bond with religious voters. It didn't hurt that movement conservatives love conversion stories, either.
As Kilgore notes, McCain seems to be doing the same thing--converting his heretical period into the first act of a redemption tale about family, faith, and patriotism. This may or may not help McCain in the general election. But what does it say about John McCain, potential commander-in-chief?
Converts, it's well known, don't always shuck their pathological tendencies when they take their vows. As Justin A. Frank and many and others have speculated, George W. Bush may have kicked the bottle, but his thought processes retained the recklessness and tendency to absolutism which characterized his earlier shenanigans. Likewise, even though John McCain plotted a direct course from the Keating Five to his crusade for campaign finance reform, he's still admittedly prone to recklessness and serious lapses of judgment.
Given that traits exhibited at the age of fifty are reasonable indicators of character, I'll match Kilgore's assertion that McCain's callowness "persisted well into late-middle-age" and do him one better: once callow, always callow. By playing up his "Prodigal Son" persona, McCain is dressing up that character flaw with poetics and, incredibly, making it central to his bid for the American presidency.