Tonight's town hall debate at Hofstra University will work a little differently than the previous presidential and vice presidential debates. Here's what to expect.

There will be no opening (or closing) statements from President Obama and Mitt Romney; moderator Candy Crowley will introduce the candidates. Then town hall participants, undecided voters selected by the Gallup Organization, will start asking questions. Romney gets the first question.

 After each question, both candidates get two minutes to respond. Crowley will then ask a follow-up question. The candidates will have another two minutes total to discuss, but that time can be extended at Crowley's discretion. The Presidential Debate Commission is hoping to get through 13 questions.

Both campaigns objected to Crowley's intention to ask follow-up questions, having agreed themselves that she would not do so. But that agreement did not include Crowley or the commission.

 In all, there will be 82 town hall members on the stage. Only Crowley will know the questions in advance. The town hall participants have already submitted their questions to her. With a small team of helpers, she's chosen the people who will get to speak and the order in which they will do so.