Obama contributes to campaign fund he didn't use

Overall, Democratic primary candidates spent $2.6 million in 2008 while Republicans used $17.5 million of the fund. Each party received about $17 million for their conventions. 

Before 2008, the previous spending low was $133 million and has ranged from $73 million when the fund was established in 1976 to the high in 2000. The amount was increased from $1 to $3 in 1994. 

Public participation has declined from a high of 28.7 percent in 1980 to a low of 8.3 percent in 2007, according to the latest figures from the FEC. 

Candidates become eligible for funds once they have raised $5,000 in 20 states. Only contributions from individuals are matchable and only $250 of each person's campaign contribution can be applied toward the $5,000 threshold in each state. Only $250 of that contribution is ever matchable, according to the FEC.