If at the time of a certification by the Commission under section
9005 for payment to the eligible candidates of a political party, the Secretary determines that the moneys in the fund are not, or may not be, sufficient to satisfy the full entitlements of the eligible candidates of all political parties, he shall withhold from such payment such amount as he determines to be necessary to assure that the eligible candidates of each political party will receive their pro rata share of their full entitlement. Amounts withheld by reason of the preceding sentence shall be paid when the Secretary determines that there are sufficient moneys in the fund to pay such amounts, or portions thereof, to all eligible candidates from whom amounts have been withheld, but, if there are not sufficient moneys in the fund to satisfy the full entitlement of the eligible candidates of all political parties, the amounts so withheld shall be paid in such manner that the eligible candidates of each political party receive their pro rata share of their full entitlement. In any case in which the Secretary determines that there are insufficient moneys in the fund to make payments under subsection (b), section
9008(b)(3), and section
9037
(b), moneys shall not be made available from any other source for the purpose of making such payments.