She is going to support Obama.
Here are her reasons:
1. She's concluded that Obama has a chance of winning the nomination.
2. She listened to the speech that Obama gave a week ago Obama's MLK Speech
The message of hope resonated with her.
3. The Clintons' mudslinging has turned her off from Hillary's campaign.
Bonus: why style matters: She heard Obama on the radio, and they played a nasty attack from Bill for Obama to respond on it.
My wife liked the graceful way in which Obama dealt with the personal attack from the Clintons.
Edit note: The speech was given a week ago, not a month ago. I corrected the text.
Now the background on my wife.
My wife is very pragmatic. She doesn't get swayed by emotional appeals.
Her main goal is to have an electable person for the general election. She doesn't want another Republican president.
My wife should have been a natural supporter for Clinton. The main reason she didn't support right away is that she perceives that Hillary is so hated that she can't win the general election.
We don't have TV, so her ideas about Hillary's chances are not painted by the media. Her impression is created by the way in which her conservative friends have periodic irrational rants against her.
But the reasons on the top were the reasons why she decided for Obama. Hillary's negative campaign seems to stress all what makes her unlikable, in my wife's eyes.
Hillary's negative campaign seems to be backfiring on her.
Just for the record, I am still sticking to Edwards until the end. :)