Bush has not "set a trap" for Kerry...
Kerry instead has fashioned his own trap and Bush is simply doing the logical thing of inviting him to jump in it. After all, it was Kerry's incessant flip-flopping and speaking on both sides of innumerable issues that has kept him a fuzzy cipher to most voters.
All Bush has done is sieze upon Kerry's own inadequacy.. his self-constructed flip-flop trap.. and force Kerry to own up to SOME stand on issues already.
Bush didnt have to plot and plan and do deep strategizing to forge this "trap".. all he had to do was take the siituation and shout it out loud and often and not let Kerry wriggle out of his own self-imposed vacillation.
Kerry set his own trap by his constant flip-flops. Now he's either going have to publicly proclaim where he stands, or flip flop once again (for each issue) in the debates.
He has been getting away with this stuff because the MSM hasn't nailed him down (when he finally chose to hold a press conference) but there won't be anywhere to run during the debates.
He either chooses a position, and loses some of his base, or he flip flops once again in front of national audience.