The NY Times offers this report. My own view on the situation, as summarized in this post at the Wall Street Journal law blog, is that it will take a 2/3 vote of the Senate to expel Burris, should he present himself to the Senate. (That is, I don’t think the Senate could exclude Burris on a majority vote, given the holding of Powell v. McCormack.) However, Jan Baran is right that the Senate could drag on an investigation before seating Burris for some time, and there’s a chance for a lengthy court fight before that if the Illinois Secretary of State refuses to certify Burris’s appointment.