Considered + object. Used when the subject should be just another name for something. Literally, that the object is the subject. He should be considered our leader since he makes all the decisions. = He is our leader. Considered + as + object. Used when the object can be used to replace the subject. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.