Judd Legum and David Sirota say yes. But really? Did he? All the available evidence -- and Legum/Sirota round up just about all of it -- seems to rest on 1) Ken Mehlman's Power Point presentation advising the president to "focus on the war" and 2) the infamous Saxby Chambliss ads in Georgia. On 1), if you read the actual presentation, the real strategy was to "focus on the war and the economy", which seems less devious and pretty standard. 2) is a better point, and the Chambliss/Bush campaign against Cleland was vicious, but as Michael Crowley argues, Cleland was a horrendously weak candidate. A more skilled incumbent would have easily fended off Chambliss, and the Osama ad would never be an issue.
So if by "politicizing the war on terror" you mean "using terrorism unfairly as an election issue," the record is pretty weak. More persuasive, I think, is the point made in All the President's Spin that Bush rather deftly tied his tax cuts to terrorism national security. (Remember Karl Rove: "This is a war and we need to make an ongoing commitment to winning the effort to repeal the estate tax.") But you would need some better polling data to prove that this tactic actually worked -- both in intimidating members of Congress and in swaying voters.
Alternatively, you could argue pretty forcefully that the president hasn't so much politicized terror as he has abandoned a coherent counterterrorism strategy in favor of a politically shrewd one. Pakistan is the obvious example here. A far-sighted president would spend his political capital solving the Kashmir crisis, draining the swamp there, and putting Pakistan on a path towards stability. (K. Shankar Bajpai probably has it right when he notes that Musharraf's support for Kashmir terrorism has fostered "domestic extremism" -- not something we want for our budding nuclear allies.) But of course, it's so much easier to pressure the ISI to nab "high-value targets."