The reality is, most leftists are open borders for moral reasons, whereas the Big Business types are happy with mass immigration because it provides a neverending supply of cheap labour.
So you just repeated everything, in a nutshell (your dwelling place) that I have said. Bravo, retard.
I mean except for your use of the term leftist, which is quite different from "Liberal" (quite different, and I think you'll find that commies are actually quite protective of their borders in both directions though).
What you're missing is the guise used by one political party in order to align with the actual policies of the other. You may, from afar imagine that Republicans have been anti-immigration but then tell me what exactly the Bush (43) administration did when it had control of both chambers, to curb immigration.
Republican rank and file don't make policy - Corporate whoring representatives do. The conservatives that count, not the fools in the rank and file (social conservatives) are run by the business community. All the dog and pony show crap is just to keep the votes coming. And, Dem political leaders can appeal to the bleeding hearts in the rank and file successfully - it creates a nice division among the voters, but the people who really matter, the ones who pull the strings are well aligned and win either way.
Interestingly, Cato Inst (very conservative), shows that Dems have historically conducted more deportations than Repukes.