Constitutional FAQ Answer #86
Q86. "How much power does the VP have in the Senate? I understand he is the President of the Senate and can cast a vote only in the event of a tie."
A. The Vice President is the President of the Senate, and as such, has the power to preside over any session of the Senate. I'm not exactly sure how powerful that makes him, though the Rules of the Senate do grant the President a lot of procedural power. He does only have one opportunity to vote (to break a tie); and he is the presiding officer in any impeachment except that of the President.