Sen. McCain, R-Ariz., the Republican presidential front-runner told CNN Tuesday he would be ready to embrace the 16-month withdrawal timetable of Democratic putative presidential candidate Sen. Barack Obama, D-Ill., provided top U.S. military commanders approved it first.

McCain's decision transforms the presidential race and gives him an unexpected boost at the very time Obama looks surprisingly vulnerable.

McCain's demand to boost offshore oil, drilling, and expand the use of coal and nuclear power to produce electricity has thrown the Democrats into confusion: Obama's alternative energy platform is vague, impractical and poorly thought out by comparison.

But as long as McCain hung tough on Iraq, Obama had a sure playing field on which to meet and beat him: not any more.

McCain has proven an unexpectedly tough, fighting and resilient presidential contender for the worn-out and discredited Republican Party. But McCain's biggest vulnerability by far so far in the 2008 U.S. presidential election campaign has been his oft-repeated determination to stay the course in Iraq.

That policy, however, received a mortal body-blow last week when Obama visited Baghdad and won the enthusiastic public support of Iraqi Prime Minister Nouri al-Maliki for his 16-month plan to pull out all U.S. combat forces from the country.

Suddenly McCain and Bush were both outflanked. The supposedly complaint and dependent leader Bush had installed to run the Shiite-dominated central government in Baghdad had defied his master and made common cause with Obama instead.

Bush, who has never seen any real combat in his life, remains determined to stand fast, defending an impossible position, even though every U.S. military leader knows that 160,000 American troops cannot possibly stay in Iraq if the government of that country and its hundreds of thousands of armed soldiers and police – trained and equipped by the Americans themselves, all want them out.

Yet Bush appears determined to remain "the Boy in the Bubble" till the day he is finally forced out of the White House and in sad truth, there is no surprise there.

Yet it was McCain, not Bush, who was ready to reverse course when reality finally hit him in the face: his reversal of position on the timetable pull-out Tuesday is of enormous importance. It means that a full U.S. withdrawal from Iraq is finally assured and has become only a matter of time. Both the main presidential contenders now agree on it.

McCain has now completed the job Obama began of marginalizing Bush. However much the president pouts or postures, even he now has to know that as soon as he leaves the White House, preparations to abandon his disastrous keynote policy, the one on which he staked all his ambitions and hungered-for historical reputation, will be thrown out the door after him.

Win or lose the presidential election, McCain has justified his "Top Gun" reputation.