America’s Majority Foundation released on Wednesday a report, “Border Wars:The Impact of Immigration on the Latino Vote.” It details what’s at stake for the Republican Party in the current immigration debate. Not to put too fine a point on it: What’s at stake is Congress, the presidency, and the viability of the Republican coalition for a generation to come. Those who have bought into the protectionist line in respect of the immigration debate might not like this study’s conclusions. Here, we’re thinking particularly of the Republican presidential candidates, among them Rep. Thomas Tancredo, Governor Romney, the former senator from Tennessee, Fred Thompson, and even — not as abjectly as the others but more than we’re comfortable with — Mayor Giuliani.

To a greater or lesser extent, they have lent credence in recent months to the idea that immigrants are primarily a burden on the American economy and social fabric — worthy to be treated as little more than criminals, to be rounded up and deported. That last point has not been made by Mr. Giuliani, but he’s lost the open tone he took on this topic as mayor. Those who have taken a protectionist position as a matter of political convenience in the GOP primary — as we expect at least some of them have — they might do well to think about the implications down the road.

“If the Republican Party renounces comprehensive immigration reform in favor of ‘enforcement only,’ Democrats will capture New Mexico, Nevada, Colorado, Florida, and Iowa in the upcoming presidential contest,” said America’s Majority Foundation research analyst Richard Nadler, upon the release of the study. The claim makes intuitive sense to anyone who’s been watching the way the political winds have been blowing. The growing Hispanic population in the interior West could easily turn the region a solid shade of blue if the national GOP keeps working overtime to alienate immigrants. And other states with large immigrant populations, such as Iowa and Florida, will be affected by the same trend.

America’s Majority Foundation has backed this intuition up with data. The foundation studied six border districts — in New Mexico, Arizona, California, and Texas — and looked at the actual votes cast by Hispanic voters in 2004 and 2006, during which period exit polls showed the GOP losing 14 points with Latinos nationally. “In the Latino areas where candidates advocated a variant of ‘enforcement only,'” Mr. Nadler said, “support for Republicans dropped by more than 21 percentage points over a single cycle, and support for Democrats rose by an equivalent amount.”

These are stark numbers, but there’s nothing surprising here. While some Republicans believe they can avoid alienating all Latino voters by focusing only on “illegal” immigration, immigrants of whatever status get the message: Hispanics go home. As Mr. Nadler puts it: “Policies that induce mass fear in illegal aliens induce mass anger in legal aliens because of ties of family culture and a shared media communication.” A solution, however, beckons. It turns out that for Republicans willing to match border enforcement with allowing those already in the country a path to citizenship, much of the political damage can be erased.

The America’s Majority Foundation study also found that where Republican candidates supported comprehensive immigration reform, Republicans lost only about 4 percentage points — a change more in line with the ground Republicans lost with the American electorate at large. For our part, we require no convincing that immigrants from the shores of all lands should be welcomed to America with open arms as lovers of liberty and eager workers ready to continue the building of America. For those who think we can and should shut our doors, however, and for those who believe political points can be won by demonizing undocumented immigrants, this study will give more than a moment of pause.