Many Republicans in Congress oppose immigration reform for fear of it creating millions of new Democratic voters and putting the White House forever beyond the GOP’s electoral reach.

That conviction helps explain the party’s opposition to a path to citizenship for undocumented immigrants. But there are at least two reasons to doubt the Republican assumption. One is that any plan with a chance of enactment will contain a very long timeline for naturalizing the nation’s 11 million illegal immigrants. It is folly to predict how the nation, let alone particular voting blocs, might tilt in the 2028 or 2032 presidential elections.

The second problem is the numbers themselves. Even if all 11 million of these people had magically been made eligible for citizenship in time for last year’s presidential election, there is no evidence they would have had a major effect on the outcome.

One of the most careful studies of that theoretical effect was performed by Carson Bruno, a researcher at the conservative Hoover Institution at Stanford University. Mr. Bruno’s analysis suggested that large-scale naturalization in advance of the 2012 elections would have added less than 1 percentage point to Obama’s margin of victory.

Fear of losing electoral ground is certainly not the only factor driving Republican opposition to immigration reform. Many Republicans believe that any form of amnesty is unfair to would-be immigrants who legally entered the country. Some think legalizing the status of undocumented immigrants would sap the economy, or drive down wages for native-born workers. In some cases, old-fashioned racism may also be a factor.

Politicians being politicians, though, plenty of Republicans are simply weighing the political risks. In doing so, they should make a clear-eyed assessment.

The Washington Post (Dec. 1)