Facebook has devoted a lot of energy to becoming an important part of the political ecosystem in America. It has conducted experiments with media partners like ABC, operated a voter registration drive which signed up 50,000 people, and promoted politicians’ fan pages and virtual gifts throughout election season.

As Facebook has demonstrated its potential to make a difference in the way political influence spreads at the grassroots level to large numbers of people, candidates from the local level to the highest levels have taken notice and spent significant time investing in their Facebook presence and communicating with their Facebook supporters.

The Obama campaign, however, also spent time with the Facebook sales team. A new report from ClickZ analyzing the Obama campaign’s Federal Election Commission filing shows that Obama spent a total of $467,000 on Facebook – $370,000 in September alone. ClickZ says the McCain campaign did not break out individual online ad spending in its FEC reports.

While these numbers are small in light of both Obama’s overall spend on the campaign and Facebook’s estimated $300 million in 2008 revenues, it’s quite likely that Facebook outpaces much other online ad spend in terms of measurable engagement for political marketing campaigns, and likely ranks pretty decently when compared to other political marketing tactics like robo-calling, which is apparently completely ineffective but still sells for $20 CPM.

If Facebook continues to educate the market, it could see bigger pieces of the political spend in upcoming election cycles.