ROCKY RIVER, Ohio  Senator John McCain said Monday that he needed to convince the American people that the troop escalation in Iraq was working and that American casualties there would continue to decline. If he did not, he said, “I lose” the election.

“Is there any doubt?” Mr. McCain said to reporters on his campaign bus.

But then he pulled back from his blunt assessment. “Let me not put it that stark,” he said, explaining that he believed people would judge his candidacy on his ability to handle the economy, which has emerged as a pre-eminent voter concern, as well as on national security.

Nevertheless, Mr. McCain, the presumptive Republican presidential nominee, made clear that he believed his prospects in November would rest in large measure on the way the situation in Iraq played out.

“If I may, I’d like to retract ‘I’ll lose,’ ” he said. “But I don’t think there’s any doubt that how they judge Iraq will have a direct relation to their judgment of me.”