A presidential campaign is a war of words, not all of them completely accurate, and trying to sort truth from half-truth has traditionally been our job. But the claims and counterclaims of the 2008 candidates now flow, tsunami-like, on blogs, video, talk radio and e-mail.

To help our readers stay on top of this information, we introduce The Fact Checker, the place to go for impartial refereeing of campaign rhetoric.

The Fact Checker will examine controversial claims and statements involving important national issues, including the war in Iraq, immigration, health care, social issues, the economy and the records of the various candidates. It will appear in The Post and at washingtonpost.com.

When we come across a statement at variance with the facts, as best we can establish them, we will point it out. When we find that something is subject to several interpretations, we will also point that out. And whenever possible, we will make a judgment, symbolized by the figure in folklore -- and Walt Disney movies -- most associated with something less than the truth: Pinocchio.

Our official Pinocchio rating will rate candidates' statements on a scale of one to four.

On occasion it may not be possible to render a snap judgment because the issue is complex or there are strong arguments on both sides. In such cases, we will withhold our judgment until we can gather more facts.

We will use this column and our companion Web site feature to try to shed as much light as possible on factual controversies that are not easily resolved.

All judgments are subject to debate, second-guessing and criticism from our readers and interested parties -- including the campaigns -- and will be revised if fresh evidence emerges.

We invite you to continue the discussion on the Web, and to suggest subjects to fact-check, at http://www.washingtonpost.com/factchecker. Significant new fact-check items will also be posted on The Trail, our daily diary of Campaign 2008.