Every million dollars counts now, especially for Senator Clinton's campaign.  However, much as she might want to economize, I suspect that there are a variety of "fixed costs" that her campaign cannot or will not dramatically cut, such as payroll.  (I presume that she has already cut the staff as much as possible without compromising effectiveness.)  How big are such fixed costs, and how do they compare with Obama's?

OBAMA: In its FEC monthly reports, the Obama campaign has reported "payroll" expenses of slightly under $2M for the past three months (April, March, February), and "payroll taxes" of about $200K each of those months (as well as "taxes" of about $345K in April only).  This amount of payroll tax seems about right, since a firm's contribution to Social Security and Medicare adds up to a bit less than 10%.

CLINTON: By contrast, the Clinton campaign's monthly FEC reports are much more difficult to understand.  In the past three months (April, March, February), the Clinton campaign has reported "salary" expenses of about $1.5-$1.6 million, which compares favorably with Obama's payroll.  However, Clinton's spending on "taxes" far outpaces Obama:

OBAMA
FEB PAYROLL TAXES

  224,939.00
MARCH PAYROLL TAXES

  219,588.23
APRIL PAYROLL TAXES

  189,921.33
APRIL
TAXES

  345,717.00
(there were no "taxes" in Feb or March for Obama)

CLINTON
FEB TAXES

  911,603.73
MARCH TAXES

  725,295.59
APRIL TAXES

  1,103,566.47

If we subtract Obama's April tax figure from Clinton's April tax figure, we are left with net taxes of about 750K, which is consistent with the March figure.  I am left to infer that Clinton paid payroll taxes of about 900K in February, after which she has paid between 725K and 750K.  This means that Clinton's REAL monthly payroll is about 7.5M compared to Obama's 2M, a consistent difference of over five million per month.

I am not particularly plugged in to know -- is this difference well-reported?

What is Senator Clinton spending that money on?  It's a bit mystifying, since under this story she is paying salaries (for which employer taxes must be paid) in excess of five million beyond what she has reported.  Where is that 5+ million being hidden?  Perhaps in the phone bank (1.9M in April) or polling (1.3M in April) or travel (5.1M in April)?

Perhaps there is another plausible interpretation of these "tax" expenses beyond payroll?  If so, I apologize in advance for suggesting that the Clinton campaign might be hiding something here.