Yesterday, Sen. Marco Rubio, R-Fla., spokesman Alex Conant caused a bit of a stir when he argued against granting permanent legal residence to illegal immigrants by claiming, “We haven’t had a cohort of people living permanently in US without full rights of citizenship since slavery.”

Leaving the merits of this argument aside for a second, it is important to recognize that this is a very common argument on the left. For example:

The Center for American Progress has an entire paper entitled, “America Should Leave the Creation of Permanent Underclasses in Its Past,” that reads, “After the nation’s founding, lawmakers stipulated that American citizenship excluded both free and enslaved Africans, who comprised roughly 20 percent of the entire U.S. population in 1776.”

San Antonio Mayor and 2012 Democratic National Convention keynote speaker Julian Castro told the The Christian Science Monitor, in reference to immigration and slavery, “Throughout the history of this nation, the biggest challenges we’ve faced have been when we created second-class citizens, much less second-class noncitizens. And so I believe that a path to citizenship is the best option.”

Coalition for Humane Immigrant Rights of Los Angeles executive director Angelica Salas told The New York Times, “Since the end of slavery we have not created a second class of Americans and we should not start now.”

Not only is Rubio’s permanent-residents-are-slaves argument a leftist talking point, but it is also dead wrong.

For starters, Rubio’s bill doesn’t even solve the problem. Only 40 percent of the illegal immigrants who received permanent legal resident status through the 1986 amnesty went on to obtain citizenship. That means, by Rubio’s leftist logic, 60 percent of those who took advantage of the 86 amnesty are still suffering as slaves in the United States today. And Rubio has repeatedly bragged that his path to citizenship will be tougher than the 1986 path. That means even fewer currently illegal immigrants will go on to become citizens under Rubio’s plan. How dare Rubio propose a plan that creates millions of new legal-resident slaves!

More importantly, there just is no comparison between slaves, who were brought and kept here against their will, with immigrants who came here and stay here by choice.

Rubio’s strategy for passing amnesty through the Senate is becoming clear: pick as many K-Street-moderate Republicans off with goodies for their home-state businesses as possible, and portray the rest of his Republican caucus as retrograde racists.

The conservative movement deserves better leadership than this.