Here's the most straightforward explanation I've seen of what's underlying Obama's blunders on FISA:
The real quandary for Obama is that he has to win the "low-information voters" in November in order to win the election, but he needs the "high-information voters" now in order to field his grassroots operations leading up to November. Low-information voters are never going to understand FISA. It is a subject that takes time and energy to master. Low-information voters look at FISA and only see the ability or inability of the government to investigate potential terrorists. Yet a large number of high-information voters in both the left and right wing of politics understand that this is much more than an issue about national security -- it's an issue of balancing national security and individual rights. At the same time, most low-information voters only understand that FISA relates to national security. In other words, low-information voters are susceptible to fear mongering on this issue...
Because Obama needs to win low information voters in November, and many of them will be fooled by scare mongering from the right, many are interpreting the strategy as a short term sacrifice for a long term gain -- Obama sacrifices the FISA vote today to save us from a McCain-picked SCOTUS tomorrow that would uphold the FISA vote. Some are even suggesting that an Obama-picked SCOTUS would rule that the current FISA bill is unconstitutional under the Fourth Amendment.
What this doesn't take into account, of course, is that if Obama chose to LEAD on this issue he could CHANGE that calculus. He has the intelligence and communication skills to get the essence of this issue across to those low information voters if he chose to make it a priority.
By choosing not to make it a priority he's going along with the conventional wisdom that says those voters can't be educated, that this issue can't be properly explained. If he chose to make it a priority he could CHANGE the lack of public understanding of the issue. He could CHANGE the Republican framing. He could CHANGE the ignorance that lets fearmongering work on those low information voters by helping them understand how dangerous and un-American this bill really is, for the Consititution and for their constitutional rights and personal privacy. He could bring CHANGE, but instead he's turning away from the opportunity because it's a risk.
CHANGE that's worth anything always brings a risk. Every potential CHANGE he might be called upon to lead on isn't worth its inherent risks. But if the fight on FISA isn't worth those risks I don't know what is.