McCain's Scorched Earth Strategy

When after the Republican convention, Obama's poll numbers momentarily slipped behind McCain's, panicky Democrats urged him to get mad. He did precisely the opposite. He got calm. While critics derided his reserved demeanor and wondered why he didn't land any knockout punches in the first debate, Obama knew all along what that what he needed to do was not put on an entertaining fight but offer reassurance in troubled times.
In contrast, the McCain campaign is opting for a road show with all the dignity of a pro wrestling tour, sending Sarah Palin out to accuse Obama of "palling around with terrorists." Even Fox News has taken notice of the ugly tone the McCain/Palin rallies have taken:

You'll hear the booing behind me. In recent days, when Barack Obama's name has been mentioned, it has gone from boos and hissing to actual chants and calls of traitor, criminal, and even terrorist.
The McCain campaign says they don't condone it, they don't want to see it happen, but it's happening more and more every day.

Nate Silver of FiveThirtyEight calls it "a sad denouement for what was to be a high-minded campaign focused around themes of honor and reform."
John McCain's campaign took on a darker tone when Steve Schmidt, an acolyte of Karl Rove's slash-and-burn politics took the helm of the fabled Straight Talk Express. John Heilemann writes in New York Magazine that McCain's handlers have lost the distinction between strategy and tactics:

The irony here is that, for so many months, the campaign being waged by Schmidt & Co. was viewed by the press as devious, sure, but deviously brilliant, delivering to McCain innumerable victories in the battle for the daily—and even hourly—news cycle.
McCain may have won some news cycles, but he is losing the contest of the meta-narrative—and with it, perhaps, the election."

What will it profit a candidate if he gains the news cycle and loses the election? It's hard to change voters' views when changing tactics so frequently. But the problem for the McCain campaign is even more fundamental.
David Kuo writes, "John McCain has no real idea why he should be president." McCain "knows that he has grueling contempt for his opponent" and "is a better, more tested man," but on policy "is intellectually, philosophically, and politically vacuous."
Voters who look at campaigns for clues as to how the candidates would govern, are not being reassured by McCain's increasingly angry demeanor. He could hardly bear to look at his opponent in the first debate, and dismissively referred to him as "that one" in the second. While his campaign is trying to shift attention to Obama's character, voters increasingly like the steady cool of the young senator compared to his older colleague. It will be even more difficult for John McCain to bring his opponent down a few notches while restoring the luster to his already tarnished reputation as a bipartisan maverick. The McCain campaign will have a lot of scorched earth to cover in the next 25 days if they want to turn this around.