For me, being able to hold a politician accountable is having the real power to actually have a negative impact on something they really care about, namely getting elected and passing legislation they want to pass (although there might be a few other smaller things some politicians might care about). Unless you have the ability and willingness to mess with a politician in a serious way on either of those things, I don't think you can hold them accountable. I don't think saying bad things about them holds them accountable, I don't think holding a protest holds them accountable, I don't think starting a petition holds them accountable- unless it is affecting their ability to win an election or pass legislation.
I'm not saying you shouldn't say bad things, hold protests, start petitions- those are all fine things to do, especially if they help you build a long-term movement. But we should be very honest with ourselves about what we are doing and why, and we should understand when we actually are doing something related to holding politicians accountable and when we aren't. It all relates to how much power you have, how much you can build, how much you can leverage.
I say all this to bring me to my main point: in all my years of organizing and working to build progressive power, I have come to the conclusion that there is literally no acceptable way of holding a Democratic Presidential candidate accountable in the last few months before a general election. Perhaps it's because I'm just not a creative enough person, but I can't see how to do it.
Progressives hold a potential Presidential candidate accountable in the years before they decide to run because those candidates know they might need progressive support in a primary fight. We can hold them accountable all through the primary process because there's always another candidate that can be helped, or you can hurt their general standing with the Democratic voters they need. We can hold Senators and House members running for re-election accountable because there are tons of other races you can give your money and talent and other resources toward. You can sometimes hold the Democratic leadership accountable by throwing roadblocks in their way while they are trying to push legislation through.
But the only way to hold a Presidential candidate in the general election accountable once the general election season comes around is to work for their defeat or otherwise endanger their victory. For most of us, given the alternative of four more years of deadlocked government and a stubborn, hyper-aggressive President McCain, that is not an acceptable option. I see occasional commenters writing about not lifting a finger to help Obama now that he's screwed us on FISA or other issues, but I don't think very many of us in the progressive movement are there. Am I bummed, am I pissed that Obama and most of our Democratic leaders caved in on FISA? Absolutely, and there's nothing wrong with saying so. But am I going to "hold Obama accountable" for this action? Well, no, frankly. I don't think there's a way to do that without doing something far worse. It's the nature of the American political system: winner take all, no instant runoffs, no fusion voting (except in a few states). In the months before a Presidential general election, I can't think of another alternative re the Presidential race other than doing everything I can do to help Obama win.
I will admit right now that this is a place where the old-school politico in me takes over: I see no choice other than to be totally, thoroughly in the tank for the Democratic Presidential nominee in the five months before the election. I'm happy to join with Matt and Chris and the progressive netroots on many things- progressive primary challenges like Lamont and Donna Edwards; exposing the Bush Dogs; taking on Democrats when they screw up on issues in general; hammering away at Dems to do the right thing when tough votes come down. All of those tactics are ones I'm down for. But in the last five months of a Presidential general, I get totally focused on one thing: winning the damn election. The stakes are simply too high. Winning the election won't solve all our problems, or give us a suddenly progressive America, but it at least gives us a chance to make progress. If I have to swallow my anger on an issue I care about, well, to be blunt, I'm down for that, too.