The tone of the coverage of the departure of more McCain campaign staffers is that of everyone deserting a sinking ship, but the reality is nearly all those leaving are tied to Terry Nelson, former political director for the Bush '04 campaign, who was just fired by McCain last week along with strategist John Weaver. It's not surprising at all in that context - in fact, it should probably be expected. With the campaign tightening its belt, paid staff brought on board by Nelson may be leaving to avoid being canned.
Nelson and Weaver attempted a straddling strategy, trying to reconcile McCain's long-time "maverick" image with status as the putative "establishment" frontrunner (the latter role having been successfully adopted by Bush in 2000, Dole in 1996, and Bush the Elder in 1988). It never really fit McCain, especially after Giuliani surged to an early lead in the polls which he has not relinquished. Even more importantly, the campaign spent lavishly - Nelson had apparently planned on raising $100 million for the primary cycle (through next year), and spent as if the money was coming in on target, which it was not.
It was this spending which brought the campaign to the brink. McCain had raised 25% more in the 2nd quarter than John Edwards, but it was going out faster than it came in.
McCain is going to concentrate on New Hampshire now, returning to the personal "retail politics" of town meetings and storefronts that enabled him to win the state in 2000. While the campaign still claims he will compete in Iowa, that makes little sense at this point. Romney has poured more cash into Iowa than Ethanol has - let Rudy or Fred "stop" him there. At this point the expectations are low enough that a win or close second in NH would be an upset - just the sort of boost he will need to jump-start his campaign again.
The Reuters story on staff departures, if anyone is interested.