It has become conventional wisdom that illegal immigration may be the type of political issue that can rile voters, but perhaps not enough to change votes. And besides, the thinking goes, people far from the border really don’t care.

These skeptics about the power of the immigration issue to change votes and elections ought to think again. The focus on immigration in the TV ads blanketing Iowa should convince any doubters.

Candidates for the Republican presidential nomination are learning to read the polls – not just the horse race numbers, but the back pages in surveys that get at voters’ gut views.

Data from the nation’s three most important general election swing states clearly show that not only do voters care but politicians who cross them on this issue are taking a serious electoral risk.

A Quinnipiac University poll released earlier this month looked at attitudes toward immigration policy in Florida, Pennsylvania and Ohio, the big three battlegrounds of the Electoral College. No candidate has been elected president since 1960 without carrying two of the three.

What stands out is a consensus that cuts across party lines: Voters want immigration reform focused on stricter enforcement rather than reform that would make it easier to integrate illegal immigrants into American life. And almost a quarter of voters see immigration policy as a potential deal-breaker for them in deciding whom to support for president.

Although the issue is likely to be a bigger deal in the November election – because in general the likely Democratic nominees are less in favor of strict enforcement than their potential Republican opponents – it has emerged as a key part of the effort to stop former Gov. Mike Huckabee’s fast-rising campaign for the GOP nomination.

Huckabee has zoomed to the top in the Iowa polls, much to the dismay of former Massachusetts Gov. Mitt Romney, who had been leading. Romney’s campaign strategy has been built on the idea that he must win Iowa and New Hampshire to create momentum he needs in the larger states that follow. A loss in Iowa would make it very difficult for Romney to win New Hampshire and that would almost certainly doom his candidacy.

That’s why Romney has come out swinging hard at Huckabee and he has decided that immigration is the former Baptist minister’s Achilles heel. Romney has gone on air with commercials that focus on Huckabee’s support for college scholarships for illegal immigrants and for making them eligible for the in-state tuition break available to Arkansas residents, but not U.S. citizens who live elsewhere.

Those are not positions that Huckabee has staked out as a presidential candidate; they are part of his record as governor at a time when immigration was not the hot-button issue that it is today. Huckabee has responded with his own ads that proclaim his support for border security measures, but that do not mention the actions he took as governor – doing so would give further credence to Romney’s charges.

Huckabee and Romney understand which way the wind is blowing on the issue, even in states without large illegal immigrant populations, and that are far from the Mexican border.

The Quinnipiac survey of Florida, Ohio and Pennsylvania provide the evidence for their response. Asked whether U.S. policy on the issue should primarily move in the direction of integrating illegal immigrants into American society or stricter enforcement of the laws against them, there was little difference in the three states. On average 70 percent favored stronger enforcement, 21 percent favored integrating illegal immigrants into American society.

Voters were then asked if they agreed with a presidential candidate “on other issues,” but “completely disagreed on the issue of illegal immigration do you think you could still vote for that candidate or not?”

A sizable majority – an average of 65 percent of voters in those three states – said that they would vote for the candidate they agreed with on other issues but not on immigration. But an average of 22 percent said that illegal immigration could be a deal-breaker for them when it comes to voting for a candidate.

Of course the data mean three times as many voters don’t think it is a deal-breaker than do. Yet, the sizable number who put it in that category underscore the issue’s potential clout in anything resembling a close election.

Most interesting is that 27 percent of independents – the key swing voters who decide elections – say immigration could turn them away from a candidate, more than either Democrats or Republicans.

As we are seeing now in Iowa, immigration isn’t just an issue in border states anymore.