Gen. George Casey, the former U.S. commander in Iraq, is likely to be the Army's next chief of staff despite limited opposition in the Senate, most notably from Iraq war supporter Sen. John McCain, who has previously defended President Bush's right to make executive appointments.

McCain voted against forwarding Casey's nomination to the Senate floor during the Senate Armed Services Committee vote on Tuesday and he said Wednesday that he will oppose the nomination when it goes up for a decision on Thursday.

One of Casey's most ardent critics in the Senate, McCain blames Casey for the "dire and deteriorating" situation in Iraq. At his confirmation hearing last week, the Arizona Republican and 2008 presidential candidate questioned Casey's judgment and blamed the general for strategic missteps resulting in "unprecedented levels of violence."

He also called on Casey to "explain why your assessment of the situation in Iraq has differed so radically from that of most observers and why your predictions of future success have been so unrealistically rosy."

On the Senate floor Wednesday, McCain said Casey "more than anyone" has been the architect of U.S. strategy in Iraq, and during that time has presented false scenarios to Congress about progress of Iraqi security forces training and their ability to combat sectarian violence.

McCain, who has long advocated boosting the number of U.S. troops fighting in Iraq, added that Bush's new surge plan might need more than the five brigades that the president committed in his strategy speech on Jan. 10. Nevertheless, McCain said, at his confirmation hearing, Casey continued to say that two brigades would suffice and would leave incoming commander, Gen. David Petraeus, with "flexibility."

For his part, Casey argued that he didn't ask for more troops when the security situation began to worsen because he did not want to bring "one more American soldier than necessary" into Iraq.

Despite the decision to oppose Casey, McCain has in the past said it's the president's decision to set up his commanders and appointees the way he wants. In 2005, McCain said Bush "has a right to put into place the team that he believes will serve him best."

In a statement made at a May 26, 2005, confirmation hearing for John Bolton to be U.S. ambassador to the United Nations, McCain said that "one consequence of President Bush’s re-election is that he has the right to appoint officials of his choice."

"When President Clinton was elected, I did not share the policy views of some of the officials he nominated, but I voted to confirm them," McCain said at the time.

Asked about the contradiction, McCain told FOX News on Wednesday that his comments in defense of presidential appointments do not mean that he has abandoned the Senate's constitutional right to advise and consent.

"There's a reason not to [vote for Casey]," he said.

"There is the advise and consent clause. Nothing said we have to be a rubber stamp," McCain said, echoing Democratic objections to many of Bush's past nominees.