You can find the staff memorandum here and a staff follow-up arguing that a candidate needs a vote of four commissioners to withdraw from the presidential public financing system. (For background on the issue, see here.)
Here is the staff conclusion:

We recommend that the Commission adopt the third outcome and determine that Senator McCain may withdraw from the Matching Payment Program because he did not pledge public funds as security for private financing.
First, we believe that the Matching Payment Act does permitt candidates to withdraw after they have been declared eligible. Although no eligible candidate may exceed the expenditure limits, the statutes simply do not say whether the Commission has discretion to reverse its eligibility determination and decertify a candidate. The fact that the statutes are completely silent on the issue of withdrawal strongly suggests that the Commission should read them to be silent, or at the most ambiguous, on the issue of withdrawal under Chevron Step 2. Even though the Commission might argue that the statutes’ meaning are plain, that argument would be entitled to no deference; at Chevron Step 1, it is ultimately for a court to determine whether Congress spoke. See Chevron, 467 U.S. at 844. The Commission might also conclude that even in the face of statutory silence, a prohibition on withdrawal is the proper interpretation. Were the question ofwithdrawal a matter of first impression, that conclusion might well receive judicial deference under Chevron Step 2, for it is a more than plausible construction. But the question is not one of first impression, and under these circumstances, the Commission would be more likely to receive judicial deference if it interpreted the statute consistently with its approach in prior instances of candidate withdrawal. Courts will specifically look to past precedent when determining how much deference to give to an agency’s decision. Bush-Quayle, 104 F.3d at 453.
Perhaps more importantly, there are few if any compelling policy reasons for prohibiting withdrawal by any eligible candidate at any time. Ultimately, little if any harm was done to the public financing system by permitting the withdrawal of Elizabeth Dole in 1999 or Howard Dean in 2003. Because the public benefit in the Matching Payment Act is money, it would be contrary to the purpose of the Matching Payment Act to adopt an inflexible approach that would irrevocably bind candidates to their initial decision to accept public funds, while at the same time draining the amount of funds available in the Matching Payment Program account for candidates who do actually want them. We also believe that such an inflexible approach would discourage candidates from opting into the Matching Payment Program at a time when participation in the program is declining. This danger outweighs the danger of candidates potentially abusing the Matching Payment Program by leveraging ancillary benefits without being held to any ofthe public commitments that made those benefits possible. Considering that the Commission has only been presented with three prior instances of candidate withdrawal, it seems unlikely that the Commission will face a rash of candidates abusing the Matching Payment Program via withdrawal. Moreover, we believe that the harm the less flexible approach would do to a candidate’s interest in choosing to speak without limit would significantly outweigh any public benefit gained by binding candidates irrevocably to the program even if they have not yet received public funds.
Second, we believe that the “point of no return” for candidates to withdraw occurs at the earlier of when a candidate has actually received public funds or when a candidate has pledged public funds as security for private financing. The Commission’s regulations, at 11 C.F.R. § 9035.1 (d), make clear that the expenditure limitations do not apply until a candidate receives matching funds. When a candidate has made a legally binding pledge of public funds that the candidate is eligible to receive to a creditor, the candidate effectively has already received the funds, even if they have not yet been paid out by the Treasury. At this point, the constitutional bargain shifts. The candidate has in all but form received the very benefit provided by the statute. At that point, the candidate must be held to his end of the bargain. This conclusion also has the benefit of consistency with the Commission’s approach in prior instances of candidate withdrawal. Again, the Commission would likely receive more judicial deference because this “point of no return” was at least suggested in the Gephardt opinion and the Dean matter. See Bush-Quayle, 104 F.3d at 453.
Third, as discussed above, we believe that the phrase””pledged public funds as security for private financing” in the Gephardt opinion means scenarios similar to those reflected in the Commission’s own regulations. Even if the Commission did not have its own regulations in mind at the time it wrote the Gephardt opinion, the various analytical problems posed by attempting to apply another outside source of law such as the DCC strongly counsel against looking outside the Commission’s own regulations.
Under the above standard, Senator McCain did not pledge public funds for security for private financing and may withdraw from the Matching Payment Program. Both the bridge loan regulation at 11 C.F.R. § 9035.1(c)(3) and the bank loan regulation at 11 C.F.R. § 100.82 contemplate an unambiguous pledge of the funds as collateral and some provision in the loan agreement for the funds to be made available to the lender for purposes of retiring the debt. Here, neither the original agreement nor the “in-out-in” provision unquestionably pledges funds nor provides for any funds to be made available to Fidelity and Trust Bank. Consequently, Senator McCain never reached the “point of no return” for withdrawal from the Matching Payment Program.
In sum, we conclude that the Matching Payment Act permits withdrawal unless the candidate has actually received public funds or pledged them as security for private financing. We recommend that the Commission determine that Senator McCain may withdraw from the Matching Payment Program because he did not receive public funds nor pledge public funds as security for private financing.