On Sunday, if you searched in Google for [Green Party] you would not find the official Green Party of United States web site, which is at gp.com. Even if you searched for gp.org, Google would not show you the site.

One person complained about the issue at Google Web Search Help forums and a few days later, a Googler came in and told us why.

In short, the site was hacked and included harmful malware that could infect searchers computers. Google removes sites that include malware from their index, until the site is fixed. In addition, if sites are injected with links to unrelated site, with the sole intent of link spamming Google, Google will also remove the site from their index. That is what Google did in this case, and now the site is back in the index.

Googler, Jaime said:

Today, it seems like the spam and hack has been removed from GP.org and the site is now back in the Google index.

Forum discussion at Google Web Search Help.