Quote from Franklin C. Spinney:
"Front loading is the practice of planting seed money for new programs while downplaying their future obligations. ... Political engineering is the strategy of spreading dollars, jobs, and profits to as many important congressional districts as possible. By making voters dependent on government money flows, the political engineers put the squeeze on Congress to support the front-loaded program once its true costs become apparent. Front loading and political engineering are about increasing the flow of money; the former starts the money flowing while the latter tries to lock the spigot open."
Besides increasing funding, it has the effect of biasing spending in favor of more complex weapons systems, which are easier to front-load.
Front loading can also refer to the tendency of states to choose an early date on the primary calendar for elections.