On tonight's election debate

Britain will be hosting it's first ever televised leaders' debate this evening. It should be great, if for no other reason than that British politics prizes the parry and thrust so much more than our own. 

As for the debate, I point to this old post and repost the abstract of a paper by Blais and Perella on the effects of debates. 

Almost an entire generation of election survey data was pooled together from the United States and Canada to assess the systemic effects of televised debates. Four questions were posed: (1) Is there a general tendency for evaluations of candidates to improve or deteriorate after a debate? (2) Do evaluations of one candidate negatively correlate with changes in evaluations of opponents? (3) Do debates disadvantage incumbents? (4) Do debates advantage less popular candidates? Using "feeling thermometer" items to measure voter evaluations, four patterns are revealed. First, candidates generally gain points.The supposed mudslinging that characterizes a debate appears not to feed into any notion of cynicism. Instead, voters appear to gain an appreciation for the debaters. Second, a candidate's gain is not earned at the expense of those deemed to have "lost" the match. Third, a debate does not disadvantage an incumbent. A candidate with a record to defend stands about as much chance of benefiting from a debate as a challenger.And fourth, any evaluation gaps before a debate become narrower following a debate. This final effect, which is particularly true of American presidential debates, may reflect a debate's ability to raise awareness of less popular candidates.