With the prospect of an extended nationwide primary battle looming for the Democratic nomination that could go to April 22nd (Pennsylvania) or beyond, you have to wonder how much longer Hillary Clinton can go before she runs out of money.  While Obama may not have scored the huge upset victories he wanted in states like Massachusetts, New Jersey, New York, and California, he did accomplish something significant.  The fact that his late surge put those Clinton stronghold states in jeopardy and forced her to spend millions to avoid what would have been embarrassing losses– she spent $5 million in California alone in the final weeks– means that she has that much less money on February 6th.  Keep in mind, she raised $13.5 million in the month of January compared to Obama’s $32 million– close to a $20 million gap that will make a huge difference in the amount and quality of advertising going forward.  If those figures are repeated in February, it could essentially handcuff the Clinton campaign past next Tuesday’s Potomac Primaries in D.C., Maryland, and Virginia, where Obama is expected to do well (and will likely receive another windfall of online campaign donations to go along with the positive press).  We won’t know for sure until the official campaign finance reports are released later this month, but I think there’s a very good reason why Clinton is challenging Obama to four debates between now and March.  She needs the headlines, yes, but more importantly, she needs money.

MORNING AFTER UPDATE: CNN political analyst Gloria Borger echoes my theory about Hillary’s potential money problems.

But Obama won more states, 13, and leads Clinton in pledged delegates, according to CNN calculations. Obama also counted Missouri, a national bellwether state, among his victories, and the Illinois Democrat has been on a fundraising tear. In January, he raised $32 million, his campaign reported.

“Heading into the next states … Barack Obama has a money advantage,” Borger said. “And now Hillary Clinton wants to debate every single week because she doesn’t have the money to compete with him for paid media. I think we’ll be seeing a lot more Obama and Hillary Clinton one-on-one.”

UPDATE PART 2: In three of his ten post-Super Tuesday big questions, Mark Halperin also speculates that the Clintons may be running out of financial steam and recently may even have been forced to put their own personal money into the campaign:

1. Did the Clintons contribute millions of their own money to her campaign in the last few weeks?

8. In which remaining February states will Clinton make her stand– with travel and paid advertising?

9. What happens to Clinton’s fundraising in the wake of Super Tuesday?