> So who's lobbying against this exactly?
If you've ever come across any posts on HN regarding immigrant workers in technology (who are on the same visa, the H1B†, that the author of the Vox article was on), you will see a shockingly offensive amount contempt and hatred for highly-skilled immigrants.
To answer your question more directly, despite high support for skilled immigration reform, there are currently 2 senators who are hell-bent on making life hard for highly-skilled immigrants. One of them is Chuck Grassley, chair of the United States Senate Committee on the Judiciary, and the other is Jeff Sessions, chair of the Subcommittee on Immigration. Both senators (esp. Sessions) thoroughly hate immigrants of all kinds, and have avowed to do everything in their power to block immigration reform from passing, and the committee and subcommittee they chair are key to immigration reform passing in the Senate.
Jeff Sessions has even go so far as to write a document full of half-truths and lies, with the goal of convincing other Republicans that even the tiny trickle of high-skilled immigration now permitted is detestable, and must be put to an end. The Cato Institute has an excellent fact-based rebuttal of it: http://www.cato.org/blog/rebuttal-sen-sessions-anti-legal-im...
Opposition to immigration itself is pretty hard to believe in country like the U.S., but the opposition to economically beneficial high-skilled worker immigration, is even more shocking.
† Note: there are really no other alternatives than getting a work visa, if someone wants to immigrate as high-skilled worker. I've read ill-informed people on HN say ridiculous things like, they do not have a problem with people "coming to the US normally", but they hate to their guts anyone on a work visa. Ridiculous.