Campaigning in Ohio on Monday, John McCain continued to try to shore up his credentials as the tough on terror candidate, earning a 30-second ovation at a town hall outside Cleveland for promising to stand strong against Al Qaeda.

“We will never surrender and they will. And I want to assure you of that,” McCain told the crowd.

The Arizona senator and former Navy pilot has made national security a central theme of his campaign and has long been a vocal supporter of the war in Iraq and the troop surge there a year ago.

He told reporters on Monday that if he can’t convince the American people that the U.S. is succeeding in Iraq, then come Election Day in November, “I’ll lose.”

Immediately stepping back from that comment, the likely Republican presidential candidate said the situation in Iraq will have direct impact on how voters judge him.

It is a bit unusual for a political candidate to openly hang his fortunes on a single controversial issue, months away from an election, but the preview could indicate McCain’s long-term strategy.

Democrats are also trying to help voters judge McCain on his Iraq position. In a foreign policy speech in Washington, D.C., on Monday, Democratic candidate Hillary Clinton suggested McCain is too tied to President Bush on war policy.

“Senator McCain can’t seem to budge from the Bush approach that insists on using military force when diplomacy is needed. He has said he wants to leave our troops in Iraq, it would be fine with him, for 50 to 100 years. I would start to bring them home within 60 days.”

McCain has been hammered by Democrats since a January event in New Hampshire when he said that U.S. troops could be in Iraq for up to 100 years. Monday, he tried to clarify what he meant.

“The war will be over soon. The war, for all intents and purposes, although the insurgency will go on for years and years and years. But it’ll be handled by the Iraqis not by us. And then we decide what kind of security arrangement we want to have with the Iraqis.”

That arrangement, he said, could be similar to the one the United States has with South Korea or Kuwait.

Already, though, Democratic anti-war groups have started going after McCain, with VoteVets.org, MoveOn.org and former Democratic presidential candidate John Edwards, among others, launching a $20 million ad campaign meant to shine a light on the costs of the Iraq war and link it to the economic downturn in the U.S.

The ad shows a female Iraq war veteran saying, “This is my little boy. He was born after I came back from Iraq. What commitment are you making to him?”

Jon Soltz, chairman of VoteVets.org, said the group is targeting McCain specifically.

“When it comes to his policies of Iraq, he is no different from George Bush and from now through the election every second we get we will continue to hold him accountable for his failed policies,” Soltz said, adding that VoteVets would hold McCain accountable for trying to project “an image of strength on national security when in reality he is supporting a policy that has weakened our economy and essentially surrendered to Usama bin Laden.”

Likewise on Capitol Hill, Senate Democrats have once again scheduled a vote on legislation to get troops out of Iraq, and House Speaker Nancy Pelosi criticized the Pentagon for saying it will maintain a force of 140,000 troops in Iraq through July 2008 — 8,000 more than the pre-surge troop level in January 2007.

“The statement from the Pentagon today on troop levels in Iraq is an admission that the president’s troop surge was not a temporary measure. There will be more U.S. troops in Iraq this summer than there were at the end of 2006, when the American people demanded a new direction in Iraq,” she said in a statement. “Repeated Iraq deployments are severely straining military readiness, making our nation less capable of dealing with other serious threats.”

The Republican National Committee argued that the legislation is a losing proposition that has repeatedly failed to come close to a majority of Senate votes. Meantime, McCain argues that it is Democrats and Democratic groups that have advocated failed positions on Iraq. He says they’ve been wrong in predicting that the surge would fail and wrong in predicting no political progress could be achieved in Iraq. He also used the ad campaign to revise his criticism of unchecked spending in campaign financing.

“The smoke and mirrors of the Democrats’ rhetoric betray the negative campaign tactics of their confederates. Now the shadowy 527 groups allied with them are spending unchecked millions. For them, it’s not about what’s best, it’s all about winning. … We have to prepare now so we have the resources to respond,” said McCain campaign manager Rick Davis in a fundraising letter to supporters.

FOX News’ Molly Henneberg contributed to this report.