WASHINGTON — As America’s war in Iraq enters its sixth year, Senator McCain is hoping his fight to send thousands more American troops, a surge that has helped lower casualties, will propel him into the White House.

But Mr. McCain’s record on Iraq is decidedly mixed. If the Arizona Republican proved prescient in his calls for a military build-up, many of his other predictions and prescriptions turned out wrong. Before the war, Mr. McCain predicted a quick and easy victory, not a vicious insurgency. He issued dire warnings of Saddam Hussein’s supposed weapons of mass destruction, but didn’t read the full 2002 National Intelligence Estimate that showed gaps in the intelligence.

Soon after the March 2003 invasion, however, he began criticizing the Bush administration’s management in Iraq, and clashed repeatedly with Donald Rumsfeld, then secretary of defense. In mid-2003, he started advocating a larger American force to battle the insurgency, a strategy the White House finally approved last year. Mr. McCain did not publicly embrace or join the hard-core neoconservatives who pushed hardest to unleash the American military against Iraq before the war. But Mr. McCain backed many of the same policies.

He repeatedly urged backing Iraqi emigre groups, internal dissidents, and other proxy forces to overthrow Saddam. His hawkish views carried weight as a senior member of the Senate armed services committee, which oversees the Pentagon.

In 1998, he was among the cosponsors of the Iraq Liberation Act. The law set “regime change” in Baghdad as American policy, and mandated support to opposition groups seeking to overthrow the dictator. Among the major beneficiaries was the Iraqi National Congress, a London-based exile group headed by Ahmed Chalabi. The CIA had initially sponsored the group but broke with the leader in 1997, saying he could not be trusted. Under the new law, Mr. Chalabi’s group received almost $33 million from the U.S. State Department, until American officials found financial improprieties and ended the arrangement. Asked by the Los Angeles Times this month if he regretted backing the 1998 law, which produced few discernible results other than bolstering Mr. Chalabi, Mr. McCain said he did not. Mr. Chalabi, although initially touted by neoconservatives as a future leader of Iraq, failed to garner any significant support in elections.

Mr. McCain said that by 1998 U.N. sanctions against Iraq were “breaking down,” and Saddam had defied numerous Security Council resolutions. “Every intelligence agency in the world believed Saddam had weapons of mass destruction,” he added.

Mr. McCain cited the same reasoning when asked why he and nine other Congressional leaders urged President Bush in a letter dated December 6, 2001, to next target Iraq since the Taliban regime had collapsed in Afghanistan. It is “imperative that we plan to eliminate the threat from Iraq,” the lawmakers wrote. “We believe that we must directly confront Saddam sooner rather than later.” Later that day, Mr. McCain told MSNBC that it is “possible, if not probable, that internal opposition forces can prevail over time.” Asked if it wouldn’t require 100,000 American soldiers as occupation troops, Mr. McCain demurred. “Oh no,” he said, “I don’t think so at all.”

By the following fall, Mr. McCain offered unstinting support to the Bush administration as it sought to rally the nation for war. In September 2002, Mr. McCain told CNN that he expected “an overwhelming victory in a very short period of time.”

But Mr. McCain openly disputed Bush administration claims that Saddam appeared linked to the September 11, 2001, attacks. “I doubt seriously if there’s this close relationship between Al Qaeda and Saddam Hussein,” he told CBS News that September.

In October 2002, Mr. McCain again rose to back the Bush administration when it sought congressional approval for a resolution to use force if necessary to disarm Iraq. The Iraqi tyrant, Mr. McCain repeatedly warned his colleagues, was “a clear and present danger [to American security].”

“He has developed stocks of germs and toxins in sufficient quantities to kill the entire population of the Earth multiple times,” Mr. McCain said, according to the Congressional Record. “He has placed weapons laden with these poisons on alert to fire at his neighbors within minutes, not hours, and has devolved authority to fire them to subordinates. He develops nuclear weapons with which he would hold his neighbors and us hostage.”

In fact, none of the weapons existed. After the invasion, the CIA-led Iraq Survey Group concluded that Saddam had abandoned or destroyed his chemical, biological, and nuclear weapons programs after the Persian Gulf War in 1991, a dozen years earlier.

When the invasion began, Mr. McCain told MSNBC that he had “no doubt” that American forces “will be welcomed as liberators” in Baghdad, the Iraqi capital. But he changed his views after his first visit to Baghdad, in August 2003, as the insurgency was just beginning.

Returning home, Mr. McCain began calling for deployment of thousands more troops. The policy set him sharply at odds with the White House, his party, and military commanders. Virtually alone in Congress, Mr. McCain pushed for a larger force with growing urgency over the next 3 1/2 years as casualties mounted and public support plummeted.

The Bush administration finally agreed to send nearly 30,000 additional troops early last year, bringing the current total to about 155,000. The so-called surge has helped curb the sectarian slaughter and anti-American attacks, according to the Pentagon.