There are three kinds of advertisements that could generate income for a political blogger who isn’t getting tens of thousands of pageviews a day:

1. Cost-per-click (CPC) ads: CPC ads are displayed on your pages at all times but only earn you money when a visitor clicks on one of them. (Pay rate is generally between $.01 and $.75 for each click on my sites.)
   Placement ads: Placement ads earn you money simply for displaying them. Typically, ads like these come from campaigns and political organizations through systems like BlogAds (invite only), Text Link Ads, or AdBrite. (Pay rate varies greatly based on how much you are willing to ask for and how much traffic and respect you have earned, but base level is about $10 per week.)
   Affiliate links: Most companies are not going to come knocking on your door to buy advertisements on your blog no matter what you do. Affiliate links give you the opportunity to seek out products that you think your readers might like and place them on your blog, but you only make money when a reader actually buys the product. (Pay rate is generally 4%-30% of the price of the products purchased.)

There are arguments to be made for each of these advertising formats, and it is worth experimenting with all three.

CPC ads generate revenue almost directly proportional to the amount of traffic you receive. On the day that you get front page linked by DailyKos, you might make ten times as much money (we’re talking $5.00 rather than $.50) as you would on a normal day. There are strategies for improving the number of clicks your ads receive (many dealing with placement of ads on the page), but good content-based CPC ad networks are a steady, if small, source of income, because they are always there and require no maintenance to keep them fresh.

Placement ads are the perfect solution for any blogger who can get them. Using a third-party to list your blog and sell ad space on it helps you attract advertisers and process payments automatically (although the services to charge a percentage of ads sold). Blogs with little traffic or reputation will not attract many of these advertisers, so wait until a few people know who you are before trying to attract them.

Affiliate ads are the most hit-or-miss of the three options, and they require the most work on your part. But when you find the one product that 50 of your readers end up buying, you can make more money on this kind of advertising than on the other two combined. But most of the products you link to will not attract many buyers. (Amazon.com does now have some context-based affiliate links, which require less maintenance but are also not specifically tailored to your site’s readers.) Typically, one affiliate purchase will earn you more in a day than all your CPC ads for that day.