Tonight, President Bush will sing from Sen. John McCain’s (R-Ariz.) songbook, but McCain himself may pay the political price.

McCain has long been the chief advocate for the more-troops-in-Iraq school of thought.   President Bush will move toward that position tonight, and McCain will applaud loudly.  But Bush’s surge in troops complicates McCain’s political strategy for the White House.

McCain’s position in the Republican presidential field is complicated. He is in some sense the front-runner, but not really the establishment candidate. He has in the past been the greatest thorn in the president’s side, but has become one of the president’s strongest backers. And he has been in some ways more hawkish than the president on the war in Iraq and war on terror, but on the other hand critical of the administration’s tactics on detainees, torture and other practices. McCain’s military service, heroism, and long experience with military issues in the Congress, combined with his strategic differences with the president, make him a credible yet different kind of successor to Bush.

Put another way, McCain was uniquely set up in the Republican field to answer the question of how he would continue Bush’s legacy and how he would strike out on his own, especially when it came to Iraq and foreign policy more generally. He could say (1) “I am tough and recognize the seriousness of the war on terror;” (2) “My experience makes me uniquely qualified to run this war better than anyone else,” and (3) “I don’t think we need to compromise civil liberties and the uniform military code of justice to win this war.”

Who else in the Republican or Democratic field could make such an argument?  Who else could project the same toughness, competence and high ethical standards?

But Bush’s new surge strategy weakens McCain’s political argument that he could better handle Iraq.

If Bush follows through on any sort of surge in troops, McCain’s call for more troops will seem passé. This may be grossly unfair to McCain, as he will not control the Iraq strategy. McCain himself recognizes that just talk of surge won’t do much to change Iraq. Last week at the American Enterprise Institute, he said that “the worst of all worlds would be a small, short surge of U.S. forces.”

Nonetheless, if the Bush surge in troops does not show progress in the next 18 months, then the American public may very well say to McCain: “We tried your approach and it hasn’t worked.” McCain could argue that there wasn’t enough of a surge, not enough time, or that he would have been smarter and more competent, but his political position as a new man with a new plan will be weakened.

If the plan does show results, McCain and the country will be grateful, but it will make McCain more the candidate of the status quo, at least on Iraq. Politically, John McCain is best as a reformer, a change agent, not the loyal follower.

Despite these potential political pitfalls, McCain will likely be supportive of the president’s efforts. Bush’s new strategy will certainly have kinship with what McCain has been saying from the beginning of the war. And as a patriotic citizen, supporter of his commander in chief, loyal Republican, and ranking member on the Armed Services Committee, McCain will embrace the Bush plan. Finally, with Democrats planning to ratchet up the rhetoric against the surge, McCain’s role as Bush’s defender will be even more prominent.

Two years from now, McCain’s political fate will be as much connected to Bush’s actions as it was in 2000.

Fortier is a research fellow at the American Enterprise Institute.