How do we know that Tuesdays election was a rejection of the Democratic position, health care etc. and a mandate for the Republician opposition?

From what I have heard the right has been saying that the election of a Republican in MA, or even a close election, is a mandate for their opposition to the health care bill, the bail out and the general handling of the economy. I’ve been hearing about this for more than a week. But how do they “know” this to be true? Have any polls been done to actually ask the voters why they voted the way they did? Even here, people are making statements that the vote was a result of “national” issues, rather than a local election. Where is the data to back up this position?