By any standard, President Bush heads into his convention in a very weak position. His current position stems from the fact that voters judge the incumbent on his performance and on the state of the nation. By this measure, the president is in grave difficulty. To be counted a success, the Republican convention must fundamentally alter public attitudes on President Bush's stewardship of the country.

There are some basic benchmarks by which an incumbent's success can be measured as the campaign heads into the fall:

• The average winning incumbent has had a job approval rating of 60%. Indeed, every incumbent who has won reelection has had his job approval in the mid-50's or higher at this point. In recent polling, Bush's average approval rating has been 48%. President Bush must emerge from his convention having dramatically altered public perception of his performance in office.
  
  
• In recent years, when incumbents have gone on to victory, 52% of voters, on average, said the country was on the right track. Now, just 37% think things are moving in the right direction. Thus, President Bush must convince the electorate that the nation is in much better shape than voters now believe to be the case.
  
  
• Every incumbent who has gone on to be reelected has had a double-digit lead at this point.
  
  
• Following their conventions, the average elected incumbent has held a 16-point lead, while winning incumbents have led by an average of 27 points. Bush will need a very substantial bounce to reach the mark set by his successful predecessors.
  
  
• Incumbents have enjoyed an average bounce in the vote margin of 8 points.
  
  
• On average, incumbents' share of the two-party vote has declined by 4 points between their convention and Election Day.

President Bush has the opportunity to achieve an average, or even greater, bounce from his convention. Typically, elected incumbents go into their conventions with a 9-point lead, while incumbents who have gone on to win enter their conventions with a 21-point lead. Most current polls show the race quite close. This gives the president substantial room to bounce. By contrast, Senator Kerry entered his convention in a far stronger position than the average challenger. The average challenger goes into his convention 16 points behind, while Senator Kerry entered his convention with a 1-2 point lead. This gave Senator Kerry much less room to bounce.

However, as the data above makes clear, average is not enough for President Bush. Incumbents who went on to win reelection had an average lead of 27 points after their convention. Indeed, the average elected incumbent -- winners and losers -- had a lead of 16 points after their conventions. An average bounce would still leave Bush well below the historical mark set by other incumbents, particularly those who went on to victory.

Perhaps most important, the average elected incumbent experienced a 4-point drop in his share of the two-party vote from the post-convention polling to Election Day. Thus, to beat the odds, President Bush will need to be garnering 55% of the two-party vote after his convention. Anything less than that and the president will remain in grave political danger.

The question now is, will the media run with Mellman's suggestion the way they did with Matthew Dowd's just before the Deomcratic convention that Kerry should get a 15 point bounce? Somehow I doubt it, which is a shame because Mellman's actually make more sense than Dowd's did.

Personally, I expect that Bush will get only a small bounce from the convention, for the same reasons that Kerry's was small (in the horse race numbers, that is): there's just not enough room for a big bounce. The real question for Bush post-convention will be whether his approval numbers improve at all, or the right track/wrong direction numbers. If they do, he's got a chance to hold on, if not, he's toast.

[suggested by a similar post on The Hedgehog Report]