There are plenty of theories circulating right now–including the provocative take by James Vega here at TDS–about the origins and nature of John McCain’s recent erratic behavior.
But just over a month before Election Day, a second and arguably more pressing issue is how McCain’s behavior is being perceived by voters. Polls get in the general vicinity of such perceptions with questions about “leadership” and trustworthiness, but these categories are often just placeholders for other factors, include agreement on the issues. And at this moment, it’s unclear whether McCain’s recent slide in the polls is attributable to his behavior over the last couple of weeks, or to (a) a general refocus of the electorate on the economy, an issue invariably helpful to Democrats this year, (b) the specific Republican fingerprints all over the financial crisis and the failed bailout; or (c) simply a return to fundamental strengths and weaknesses for the two candidates after McCain’s post-convention “surge” and the boom and bust of the Palin phenomenon.
In the absence of clear empirical evidence about changing perceptions of John McCain, one theory’s as good as another. But I’d draw attention to one articulated today by Republican operative Patrick Ruffini, who thinks McCain’s behavior during the financial crisis exposed him as senatorial, not presidential:

McCain dramatically overestimated his ability to control the battle space with a single grand maneuver. It was the starkest example in recent history of a candidate gambling — and with seemingly no frickin’ clue what would happen at that — and coming up short.
But more than a misjudgment — hey, those happen all the time in politics — it surfaced a problem that should have been clear all along: McCain’s inability to create a Presidential persona apart from his legislative persona.
Announcing that you’re dropping everything, going back to Washington, and singlehandedly forcing a deal is not a Presidential thing to do, but it is a very Senatorial thing to do. Even in crisis, our Presidents have tended to project a calm, above-it-all demeanor that leaves the sausage-making to Congress, even if the behind the scenes reality is always somewhat different.
By injecting himself into the process so directly, and staking his campaign on it and eventually failing, McCain showed an impulsive nature shaped by years as the maverick of the Senate. When Americans wanted a steady hand at the helm, McCain’s behavior last week seemed not a little erratic. That’s not uncommon for Senators who always have to jockey for position — but unusual for a President.

It’s often noted how rarely senators are elected president, and that fact is often attributed to the long records legislators accumulate that offer all sorts of targets, or to voter doubts about politicians with no executive experience. But Ruffini’s hitting on something else: there is a distinctive senatorial persona that exibits itself in strange, parliamentary language; a heavy emphasis on positioning if not posturing; and a habit of showboating that becomes second nature to people who have to struggle for media and public attention against 99 fellow narcissists. None of these tendencies come across as “presidential,” especially in a crisis, and especially at a time when Congress is held in such terribly low esteem.
Going into the 2004 cycle, I recall a very smart friend expressing a preference for John Edwards on grounds that “he hasn’t been in the Senate long enough to forget how to act and talk like a real person.” As it turned out, my own candidate, the eventual nominee, John Kerry, definitely suffered from a senatorial air. One of the, if not “the,” defining moment of the general election campaign, the “I voted for the $87 billion before I voted against it” quote, was actually an inartful expression of a legitimate legislative position (the vote “for” was on a failed amendment to an underlying bill Kerry found objectionable).
McCain’s own senatorial persona has been obscured somewhat by his “maverick” reputation. But as Ruffini implies, the “Senate maverick” role is as hoary and as un-executive as any other senatorial pattern of behavior. Indeed, it may be worse when it leads the “maverick” to positions and posturings more irresponsible-looking than that of the standard-brand solon.
Like John Edwards in 2004, Barack Obama probably hasn’t been in the Senate long enough to become a complete Senator. That looked like a problem initially, particularly in comparison to McCain’s long record in Congress. But it may turn out to be an unanticipated blessing for Obama, and a curse for McCain.