Next week's marquee political event is the Pennsylvania primary, but political junkies also are eagerly awaiting Sunday's release of the latest financial reports from presidential candidates.

Those documents, along with Tuesday night's returns, will shed light on how long -- and how aggressively -- Hillary Clinton can keep competing.

What to watch for: Is she running out of money? And, even if she isn't, is Barack Obama pulling further ahead in terms of cash on hand?

At the end of February, the Illinois senator had $32 million in the bank versus $11 million for his New York rival. Sen. Clinton's balance sheet also listed debts to outside vendors of $3.7 million and a $5 million loan she made to the campaign.

The Clinton campaign already has said it raised around $20 million in March, but it hasn't said how much can actually be used in the nominating battle. Campaign finance rules make a distinction between money raised for the primaries and money raised for the general election, should the candidate make it there. Sens. Clinton and Obama have been doing both simultaneously -- but Sen. Clinton has done more.

Her campaign touted a $35 million fund-raising haul in February, but financial reports showed that only $12 million could be used in the primaries. Many of Sen. Clinton's contributors already had reached the $2,300 maximum donation for the primary campaign and were contributing to the general election, in part to boost the New York senator's monthly total. (Donor contributions for the general election are refundable if a candidate doesn't win the nomination.)

The Obama campaign doesn't face the same problem, having done a better job of using the Internet to build a grass-roots fund-raising operation. March's $40 million haul came from nearly 1.3 million donors, with an average donation of $96. "It's a lot easier to maintain a budget when you've got a million small donors," Sen. Obama told reporters last month, "compared to if you're raising $2,300 checks from people who at some point tap out."

The money gap has made a difference in the Pennsylvania campaign. The Clinton campaign said it has been outspent by as much as three to one there. And there are signs the Clintons are scrimping to hold down costs. The campaign recently has downgraded to a smaller plane and is opting for long bus rides when possible.

At the outset of the 2008 campaign, Sen. Clinton ran as a big-money candidate, Sen. Obama as the upstart. As their contest enters the final stretch, the roles are reversed. She is running as the underdog, citing the money reports.

In a fund-raising email to supporters last week, she wrote: "This race should be decided on the merits of our ideas -- not the size of our campaign coffers."