Musharraf resigned Monday ahead of likely impeachment charges. The ally of President Bush has seen his power wane in recent months following electoral victories by his political opponents.

Both McCain and Obama said Musharraf's resignation should open the door to more cooperation between Pakistan and the U.S. in the hunt for suspected terrorists.

Both candidates hailed Musharraf’s decision and the relationship between the two countries, but Obama went further by asserting that the U.S.'s most serious threats continue to come from Afghanistan and Pakistan, and not Iraq.

“I have long said that the central terrorist threat to the United States lies in northwest Pakistan and Afghanistan, and not Iraq,” Obama said in a statement. “U.S. policy must focus on assuring that all elements of Pakistan's government are resolute in shutting down the safe havens for al Qaeda and the Taliban. There can be no safe haven for terrorists who threaten the American people.”

Obama said that more than a year ago he proposed the U.S. "move from a 'Musharraf policy' to a 'Pakistan policy.’ ”

McCain also stressed that Pakistan is a “critical theater in countering the threat of al Qaeda and violent Islamic extremism, and I look forward to the government increasing its future cooperation.”

The resignation served as another foreign policy event that, like the Russia-Georgia conflict, could shape a fluid presidential race.