There are two features of the Democratic nomination process that could help Hillary.
First, Democratic primaries and caucuses allocate delegates proportionally. Candidates win "pledged" delegates based not on whether they win a state - but on how many voters support them. So, for instance, even though Clinton and Edwards lost Iowa, they still won a few delegates.
Second, about 20% of all delegates to the Democratic convention are "super" or "unpledged" delegates. This quirky provision - which does not have a corollary on the Republican side - has its origins in Chicago, 1968. In the wake of that disastrous convention, the DNC formed the McGovern-Fraser Commission to recommend improvements for the nomination process. McGovern-Fraser suggested that the process be opened to rank-and-file Democrats on the principle of "one Democrat, one vote." The reforms contributed to George McGovern (the same McGovern from the commission) winning the nomination in 1972. The party establishment did not like this. So, it added the super delegate provision to serve as a check on the party rank-and-file.
This year, according to the indispensable Green Papers, there will be 798 super delegates at the convention in Denver. They include all elected members of the Democratic National Committee, all current Democratic members of Congress (including non-voting delegates), all sitting Democratic governors, and past party luminaries (e.g. former presidents). Unlike pledged delegates, who are bound to particular candidates, super delegates are free to vote their consciences.
Here is how these rules could help Clinton.
Suppose that Clinton stumbles early, but rebounds later. By the end of the nomination period - she draws even with Obama in the primaries. She wins 45% of the aggregate vote. He wins 45%. Edwards, who in this scenario dropped out some time before the end of the season, wins 10%. That could yield the following count among pledged delegates:
Obama: 1,464 delegates
Clinton: 1,464 delegates
Edwards: 325 delegates
This leaves the 798 super delegates, who can support whomever they choose. Let us suppose, in this scenario, they divvy up the way the Hill reports declared members of Congress have so far split their support between the three major candidates: 62% for Clinton, 25% for Obama, and 13% for Edwards. That would change the delegate count to:
Clinton: 1,967 Delegates
Obama: 1,664 Delegates
Edwards: 420 Delegates
A candidate needs 2,026 delegates to win the nomination. In this scenario, Clinton goes from being tied for first to having a solid lead, and just 58 delegates short of the nomination. If she could persuade about three-fifths of the Edwards' super delegates to back her, she would win.
Now, this is not a prediction about what will happen. It is simply meant to illustrate that the rules of the nomination process give Clinton two advantages.
First, the proportional allocation rule buys Clinton time to get her campaign back on track. This is critically important. Most people assume that February 5th will be the end of the nominating season. Not necessarily. Remember that 44% of all pledged delegates will not be allocated until after Super Tuesday. Clinton could use the proportional allocation rules to keep the delegate count close through February 5th - and then draw even with Obama toward the end of the season. Perhaps as the press starts to examine him with the scrutiny that they give to frontrunners, Democrats will come back to "old rough and ready" Clinton.