In November 2007 I traveled around western Iowa with Sen. John McCain as he tried to claw his way back into the 2008 Republican presidential primary race. McCain's campaign had famously melted down a few months earlier, sending him plunging in the polls. Things didn't look good.

As we rode in a battered minivan, I asked McCain about his troubles, mainly campaign money problems and then the fallout from his stand in favor of immigration reform. Which was worse? I asked. McCain answered quickly: Immigration.

"I can show you polling numbers that it really didn't have anything to do with the financial situation," McCain told me. "As the immigration issue became hotter and hotter among Republicans, I started down."

To recover, McCain talked tough on immigration. His mantra became "secure the border first." It was enough for him to get back on his feet and eventually win the GOP nomination, despite a fourth-place showing in Iowa.

Now, potential Republican presidential candidates are making their way to Iowa again. So far Marco Rubio, Rand Paul and Scott Walker have made the trip, with Rick Santorum planning to go soon. And despite the belief in some quarters that immigration will be a less potent issue among Republican voters this time around, so far it appears to be having a serious effect on Rubio, the potential candidate most identified with the issue.

Over the weekend I emailed a number of Iowa conservatives to ask them a few general questions about the GOP field. I didn't mention immigration or any other issue; I just wanted their thoughts. What I got back, as far as Rubio was concerned, was all about immigration, and nearly all negative

"Over the last three months, Marco Rubio's name and face and voice have been so attached to the comprehensive immigration bill that it has virtually killed any enthusiasm among Republicans in Iowa for a Rubio presidential candidacy," said GOP State Central Committee member Jamie Johnson. "Most Republicans here now see Rubio as the amnesty candidate."

"Rubio seems to be so damaged it will be very difficult for him to recover here in Iowa," said Rep. Steve King. "My perspective is that the immigration issue will sort Republican candidates."

"Rubio has hurt himself immeasurably with his support of the current immigration bill," said Sioux City conservative radio host Sam Clovis. "The rule of law still trumps all the feel-good aspects of the bill."

"Immigration will be a separator issue, for sure," said Chuck Laudner, a longtime GOP activist allied with King and an influential supporter of Santorum in 2012.

Those are all opinions from the party's more conservative wing, but of course conservatives remain quite influential in Iowa. Take a step back, though, look at the whole Iowa GOP, and some will argue that immigration hasn't sunk Rubio's chances at all. The problem is, it has made him a divisive figure.

"Rubio is somewhat polarizing in Iowa," said Craig Robinson, who runs The Iowa Republican, an influential blog in state GOP circles. "Some conservatives think his push for immigration reform has ended any thought of him running for president in 2016. I am not ready to write him off. Sure, it's not going to endear him to the Steve King loyalists in the state, but he is still someone that people generally like and respect."

The bottom line is that by pushing so hard for comprehensive immigration reform, and by working so closely with intensely partisan Democrats like Sen. Charles Schumer (as McCain had with the late Sen. Ted Kennedy), Rubio has lost some of his appeal to GOP voters in the nation's first-voting state.

A candidate doesn't have to win Iowa to win the nomination. And perhaps Rubio's problems won't last. McCain made the mistake of promoting immigration reform at the same moment he was gearing up his run for president. Rubio has two years before he starts running full time. Memories might fade.

But one thing probably won't fade, and that is the conservative voter's attitude toward government. Rubio's immigration proposal is a sprawling plan that would legalize millions of currently illegal immigrants and give new powers to the secretary of Homeland Security, while promising enhanced border security within a few years. It's a promise many Republicans didn't believe a few years ago.

In '07, I asked McCain what was the most fundamental problem with his reform proposal. "What I underestimated was the lack of trust and confidence in government," he told me. "I mean, I said time after time, 'We'll enforce the borders. We'll enforce the borders. Here's X billion dollars to do it. We'll enforce the borders.' They just didn't believe us."

They still don't, and that could mean serious trouble for Marco Rubio.

Byron York, The Washington Examiner's chief political correspondent, can be contacted at His column appears on Tuesday and Friday, and his stories and blogposts appear on