With Senator Hillary Rodham Clinton and Mr. Obama locked in a tight race before Tuesday's voting, the campaign has turned into a gigantic family feud, with prominent and everyday Democrats splitting with spouses, siblings, parents and children.

A more accurate snapshot of the frosty Clinton-Obama relationship came on a frosty December day ...

... in a scorching encounter that is now known simply as "te tarmac moment." On Dec. 13, the two senators were preparing to board their private planes parked next to each other at Reagan National Airport, to go back to Iowa for a debate.

Hillary sent word to Obama that she wanted to talk to him. Obama's aides figured that she wanted to make a pro forma apology for the comments of Billy Shaheen, the Clinton co-chairman in New Hampshire, who had told The Washington Post that Republicans would pounce on Obama's confessions of cocaine and marijuana use in his late teens. Shaheen would step down the next day, but Camp Obama did not think the slam was a mere slip of the tongue.

In front of her plane, Hillary apologized to her rival about Shaheen. Obama replied that he was concerned at the pattern of insinuations and attacks from her supporters and that a message needed to be sent from the top that sharp attacks were not, as Hillary had put it, "the fun part." He brought up another recent example: the Clinton volunteer in Iowa who had been asked to leave after forwarding sleazy e-mail falsely claiming that Obama was a Muslim.

Then, according to witnesses from the Obama camp, Hillary got very agitated and was "flapping her arms."