This stuff is a bit hard to game out, but on some level, as long as Congress gives some reasonably sensible and predictable timetable for action, it's hard to imagine Wall Street collapsing. Basically, the short-term fear is that uncertainty will spur investors to pull money now, the firms won't have the capital to cover the rush, and they'll collapse. The point of quick government involvement is to reassure the markets that the firms will have the capital, and will have it quickly. This will presumably convince folks not to pull their money. But it's not clear why three days is so different than three weeks for those purposes. It would be an odd investor indeed who would pull out tomorrow, knowing that in 20 days the government is going to pump hundreds of billions into the system and the market will almost certainly lift. Most investors don't want to lose more money than is strictly necessary.
