Aware of the overwhelming public opposition to the endless slaughter in Iraq, and fearful that an eventual Democratic victor in the presidential race just might yield - albeit grudgingly, and albeit only partially - to the will of the people, Bush has just threatened the US with another terror attack should the next Prez withdraw the troops "prematurely." (the link is to the Guardian article summarizing the key points, not the actual transcript of the interview, which is a nauseating foray into Bush's daughter's wedding, Bush's (non)use of e-mail, etc.)
Undoubtedly, Bush here, as always, is serving as the mouthpiece for sectors of the military-industrial-petroleum-media-banking-intelligence-mercenary complex who are simply making too much cold cash in Iraq to let this cow go out to pasture. Plus, the US and Israel want to use Iraq to attack Iran.
By the way, these are the forces that are probably stealing US elections (not something so dingy as the Republican "Party"), because the covert operatives, ex-special forces, ex-CIA, ex-DIA people and mercenary thugs working for this vast array of huge interests probably share Bush's mostly unfounded fear of the Democrats, even though the Dems have always been as war-friendly as anyone could be. But when hundreds of billions of dollars are at stake, they figure, you can't take any chances.