AP backed off their threat of a lawsuits against the Drudge Retort (a liberal site) for quoting 40-80 words from their articles. They now say they just want to protect their headlines and the lede from being posted elsewhere. (So does that mean you can quote extensively from the rest of the article without fear of angering grumpy lawyers?)
Several websites with money have promised financial support should this end up in court in a battle over Fair Use. But stakes are high here, a ruling supporting AP could hurt bloggers.
Fair Use doctrine is vague. However too many blogs have the bad habit of quoting large sections of newspaper articles then adding a one sentence response. This is almost certainly not Fair Use and is something I avoid doing here. Besides, why would someone want to read a copy-cat blog with long quotes from elsewhere when they can read the source article instead?
A better alternative is to rephrase what the article said. Then it becomes your post, with your ideas, and Fair Use is no longer an issue.