Months ago the president of CNN/U.S., Jonathan Klein, offered a choice to Lou Dobbs, the channel’s most outspoken anchor. Mr. Dobbs could vent his opinions on radio and anchor an objective newscast on television, or he could leave CNN.

For a time, Mr. Dobbs did tone down his TV rhetoric, but on Wednesday he made a more drastic decision: He chose opinion.

Mr. Dobbs told viewers that he was resigning from his CNN job immediately. Sitting before an image of an American flag on his studio set, he said “some leaders in media, politics and business have been urging me to go beyond the role here at CNN and to engage in constructive problem solving as well as to contribute positively to the great understanding of the issues of our day.”

He remained vague about how he would contribute “to the national conversation,” saying that he was considering “a number of options and directions.”