And in so doing, John McCain set in motion within his own campaign a chain of disasterous events that served to undermine his own carefully crafted persona as the man you wanted in charge in the midst of crisis.

In rapid succession, he pivoted 180 degrees, started yelling "Fire!", "suspended" his campaign (without actually "suspending" his campaign), publicly blew off David Letterman, threatened to withdraw from the first debate and flew to DC to "save the day," which managed only to throw congressional Republicans into public division and total chaos.

Lets also not forget George W. Bush.  Bush wasn't a turning point but he sure was an underlying condition dragging McCain down.  Without Bush I don't think this would have been a "change" election.

1. Economic collapse: this is not just the bailout per se as listed in your poll, but rather the total picture: the frozen credit markets, the bailout, the way McCain handled the bailout, the way McCain was forced into talking about the economy in the debates etc. It was the whole economic picture coupled with the perception that the GOP was mostly responsible coupled with the strength of the democratic brand on the economy.

2. Press jumps into Obama's tank. It is clear that after 1. that the press started to turn on McCain. One mistake that people make in my view is that they seem to think that the press turn on a candidate because of things that a candidate does (e.g. McCain "stoppped being the McCain we knew) but this is false. The village makes up its mind and then they use whatever material is at hand to push the narrative they want and fill in the blanks. Therefore economic collapse ---> press core jumps all the way into the tank ----> 3.

3. Filling in the narrative. Once the media elite decided Obama was their man they just needed material to generate the new narrative that would help this cause. Palin is part of this. As soon as McCain's numbers started to fail it was EASY to just grab negative Palin stuff about it and beat him about the face and neck with it. The counter argument is that Palin caused problems and there is certainly some chicken and the egg stuff here, but the initial poll moves were clearly a result of the economic shift. The Palin stuff was an important but ultimately secondary effect used by the media. This was inevitable and why Palin was such a risky pick. It was always the case that if McCain's numbers started to fail that Palin would be cited as a cause no matter what she did.

"what do you think was the biggest turning point from which McCain could not recover?"

Really it was the election of GWB and the implementation in the ensuing eight years of a policy of aggressive Americanism, free-for-all markets, anti-science, fundamentalist-toned social policies and an insular demonization of opponents

Journalists Name 44th President