Any money taken in for the primary can be spent in the primary OR in the general. However, for presidential candidatesthe only federal candidates eligible for federal matching fundsyou will probably want to spend the primary money before the convention if you decide to take federal matching funds, because with the acceptance of funds comes a limit on the money you can spend in that campaign period. Obama and Clinton both rejected matching funds for the primary, so they can spend whatever they want between now and the nomination. If Obama rejects matching funds for the general, he can spend whatever he wants through November. If he takes matching funds, he won't be required to spend the money he takes in during the primary, but anything he carries over counts against the spending cap, so the incentive, if he thought he could raise the maximum amount allowable (and that won't be a problem for him) is to spend all the primary money and reload for the general.