Judgment day is Jan. 3 for arguably every presidential candidate except Sen. , D-N.Y., and former New York City Mayor (R).
No, it's not the day when it will be decided whether they go to heaven or hell, but rather the day when their futures as presidential candidates in 2008 will be judged.
With the exception of those two, a loss effectively sends any candidate to the locker room for the season.
If Sen. , D-Ill., is going to be able to stop Clinton, he has to begin with a victory in Iowa. Otherwise, her strong standing in states that follow should propel her through the balance of the schedule.
For Clinton, it would take losses in both Iowa and New Hampshire five days later to earn her a one-way ticket back home.
It's hard to imagine how she would survive back-to-back losses in states where she once led, although her lead in Iowa has never been particularly wide. Wins in Iowa and New Hampshire for Obama would make him virtually unstoppable.
It's Giuliani who has, at least on one level, a deferred judgment day.
Giuliani has never shown particular strength in New Hampshire, his early lead in Iowa is long gone, and he always has had Sen. John McCain, R-Ariz., nipping at his heels.
If there is a specific day that Giuliani must have a strong showing (other than Feb. 5, when 18 states with at least 556 delegates hold primaries or caucuses), it will be Jan. 29, when Florida has its non-RNC-sanctioned primary.
But on another level, the next week or two amounts to another form of judgment day for Giuliani.
Early on, many political operatives and analysts expressed skepticism about his chances of winning the GOP nomination based on the fact that his positions on social and cultural issues were considerably to the left of his party and because of his relatively colorful personal life.
I went so far as to boldly -- and perhaps stupidly -- say that I would win the Tour de France before Giuliani would win the Republican presidential nomination.
But while his personal history and positions on social issues have certainly hurt him, the damage hasn't been nearly to the extent that many of us expected.
He has stayed atop the national polls for almost all of 2007, and the most recent surveys have him in the mid-20s.
So, as far as I am concerned, I was wrong, whether he ends up with the nomination or not. Win or lose, Giuliani has beaten the point spread.
Having said that, Giuliani's vulnerabilities have been aired and in the spotlight over the last two weeks in a way that they never have been before.
Stories alleging that New York City police, and therefore city funds, were used to provide Judith Nathan with security while she was the mayor's mistress is a political body blow on several levels.
To the degree that his candidacy and support either show resiliency or reflect serious damage in the next couple of weeks will suggest whether these problems are as severe as many had earlier anticipated.
He faced a tough interview on Sunday's "Meet the Press" and was put on the defensive about the security story, as well as his continued holding of financial interests in Giuliani Partners.
However, his past indiscretions and flaws have not seemed to stop his momentum, and it is possible that he has the political strength to go the distance despite such seemingly fatal vulnerabilities.
From the earliest stages of this campaign it has been clear that Republican voters were really seeking a reincarnation of the late President Ronald Reagan, albeit with no success.
Every time they would focus their attention on a new possibility, the scrutiny would reveal that the new subject was no Reagan.
To be sure, this is a standard that few, if any, Republicans will ever be able to match.
After all, Democrats are still looking for a new Franklin Delano Roosevelt or John F. Kennedy.
Failing to discover a new Reagan, Republicans seem willing to settle for someone who has a chance to win and may make them feel good about themselves and their party.
Whether Giuliani is the most electable Republican candidate or not can be seriously debated, but the conventional wisdom seems to be that he is.
Whether Giuliani can make Republicans feel good about their party or not will be tested. Republicans tend to forget that not only was Reagan divorced -- many wondered whether that would be a disqualifier -- but as governor of California, he signed the country's most liberal abortion rights law. And he was still idolized by social conservatives.
Voters have selective perception. They choose what they decide to see and accept, reject or ignore.
Over the next few weeks, we are likely to see Giuliani's vulnerabilities up close, which voters will accept, reject or ignore.