Republican presidential candidate Sen. John McCain, R-Ariz., center, meets with members of Brigade 2506, veterans of the Bay of Pigs invasion, after speaking Wednesday at the Bay of Pigs Museum in Miami.

Washington ? Immigration and Iraq present opposite threats to John McCain’s presidential candidacy. The former could undercut his bid for the Republican nomination; the latter, his chances for winning the White House.

“Mistakes were made” in Iraq, the Arizona senator told Iowans one recent afternoon. “But the fact is, we are where we are.” He argues that President Bush’s troop-level increase must be given a chance to succeed because failure will result in terrorism on U.S. soil.

Minutes later, he pivots to immigration.

“We need to secure our borders. That is our first priority,” McCain says as he calls for a temporary-worker program and a way to deal with illegal immigrants already in the U.S. “We can’t deport 12 million people overnight.”

As he campaigns, McCain says his positions pre-emptively yet still faces voters’ questions. He did in Iowa and, to some extent, in New Hampshire, during bus tours last week. He returned to New Hampshire on Friday.

The two issues loom large in the 2008 race. As McCain seeks the White House a second time, he is linked to both, and each could affect his candidacy.

Long a critic of the way the war was waged, McCain refuses to waver in his support of the Iraq troop increase despite growing public opposition to the four-year-old conflict that has claimed more than 3,200 American lives. His position plays well among GOP loyalists who will choose their presidential nominee early next year; polls find a majority of Republicans favor the increase.

“His Iraq policy will not hurt him with Republicans,” said state Rep. Jeff Kaufmann of Wilton, Iowa, who is neutral in the race.

Indeed, at a standing-room-only Elk’s Lodge in Mason City, McCain gave his take on the war to a hushed audience. Some people nodded in agreement as he spoke. Those who asked questions on Iraq or commented about it tended not to challenge his stance.

“My complaint is the cut-and-run politicians in Washington. I think we have to stay in and win this thing,” Jim O’Brien, a veteran of two wars, told McCain as the crowd responded with hearty applause.

“I agree with him,” Scott Tornquist, a Mason City councilman, said later of McCain. “There were mistakes that we made, and he acknowledged that, and I appreciated that.”

McCain likely would get a cooler reception if he made the same pitch in a general election, where he would be seeking to win over Republicans as well as independents and, perhaps, Democrats. Polls show about two-thirds of people in the U.S. oppose the additional combat troops.

The senator is keenly aware he may be risking the presidency with his position, but says: “I would rather lose a campaign than lose a war.”