For the past year, Hillary Clinton's Democratic presidential nomination has seemed inevitable. She raised more money than any presidential candidate in history. She performed well in an endless series of debates. She carved out careful positions on difficult issues, protecting her left flank while not alienating moderates. She used her husband to woo crowds and raise money, while never letting him overshadow her on the hustings.

But now, just weeks before the Iowa caucuses and New Hampshire primary, the Clinton campaign has suddenly lost its air of invincibility. With Barack Obama now surging in the polls, Hillary has begun to sound not just defensive but downright shrill. While most of her early firepower was aimed at George W. Bush and the Republicans, Hillary has been taking some pretty nasty potshots lately at fellow Democrat Obama, and her campaign has unleashed the attack dogs.

In New Hampshire this week, Clinton state co-chairman Billy Shaheen told the Washington Post that if Obama wins the nomination, Republicans will exploit his past drug use to defeat him. It was a clever ploy to raise the subject of Obama's cocaine use without appearing to criticize him directly.

Obama has never tried to hide his past. In his memoir "Dreams from My Father: A Story of Race and Inheritance," Obama wrote about his struggles with identity, having been raised largely by his white grandparents after his African father abandoned him and his mother went off to pursue her own life.

"Pot had helped, and booze; maybe a little blow when you could afford it. Not smack, though," he said.

But Shaheen warned that Obama's candor would only exacerbate the problem. Having opened the door by admitting cocaine use, Shaheen said, "It'll be, 'When was the last time? Did you ever give drugs to anyone? Did you sell them to anyone?' There are so many openings for Republican dirty tricks. It's hard to overcome."

Of course the Clinton campaign isn't worried about whether Republicans will beat Obama but whether Obama will beat Hillary. And, so far, the dirty tricks against Obama have all been the Clinton campaign's. And no matter how staunchly Clinton denounces Shaheen's comments, her campaign is ultimately responsible. Continued...