The important context for the Mumbai bombings must surely be the peace initiative launched by the Pakistani President earlier in the week and seemingly moved forward by a meeting of the two foreign ministers yesterday. That makes the obvious suspects the folks who have the strongest interests in keeping India and Pakistan at daggers drawn: the Pakistani ISI (which Zardari had already stripped of its role in domestic politics) has to be the prime suspect, and apparently India has such suspicions. But there’s also the Pakistani military, al-Qaeda, the Taliban, and the Hindu nationalists.
Of all the things that might conceivably happen in the next few months, it’s hard to imagine one that would be a bigger win for U.S. long-term interests than a rapprochement between India and Pakistan. I like Jonathan’s proposal to send Biden to Mumbai or Delhi, but he shouldn’t just go on a schmoozing mission; he should carry the message that the new administration is prepared to be at least as generous in supporting an India-Pakistan deal as the U.S. has been in supporting the Egypt-Israel deal. (Yes, yes, one President at a time and all that, but as someone pointed out right now Bush is no more than about ten percent of a President, which leaves Obama stuck with being the other nine-tenths.)
Update I see Christine Amanpour reads the situation as I do.