Mike Allen of the Politico newspaper, one of the best reporters in town, quotes an unnamed senior administration official on the Massachusetts race as follows: "This is not a moment that causes the president or anyone else who works for him to express any doubt. It more reinforces the conviction to fight hard."

It is hard to believe that any seasoned political adviser would think this, or will think it for very long. That's because, in a real sense, the Massachusetts results are already in. The mere closeness of the race is in itself a stunning reversal for Democrats, even if they manage to hold the seat.

One is reminded of President Lyndon Johnson, facing a long-shot challenge from Senator Eugene McCarthy in the New Hampshire Democratic primary 46 years ago. Johnson won, but the race was close enough that he saw the writing on the wall and dropped out of the race for re-election.

Twenty years later, Walter Mondale, frontrunner for the Democratic nomination was beaten by Gary Hart in New Hampshire, and quickly recast his campaign and eventually won. Bill Clinton got a similar message in the 1994 midterms and changed course and was eventually re-elected.

These three Democratic politicians recognized what they were doing wasn't working and would lead to defeat, so they changed course. The question is whether Barack Obama will do the same. So far, the answer seems to be no.

Brit Hume is the senior political analyst for Fox News Channel.