I don’t think the rise in support is all that surprising in the wake of the Obama press conference, considering what a lousy job the administration did selling the idea up to that point. But I thought this nugget from that Rasmussen poll was interesting:

The latest data shows that support for the president is closely linked to support for the stimulus plan. Among those who Strongly Approve of Obama’s job performance, 84% favor the stimulus plan, and four percent (4%) are opposed. Among those who Somewhat Approve of the president’s performance, 39% favor the stimulus plan, while 30% are opposed.
However, among those who disapprove of the president’s performance, the results are starkly different. Just one percent (1%) approve of the plan, and 91% disapprove.

I wouldn’t put too much stock in any one poll, particularly this early in the game. And obviously there are a significantly higher number of people that are supportive of Obama at the moment than those who disapprove of his job performance. Still, the unity among the opposition seems noteworthy.