The specific Actions that were used by Americans for Better Immigration can be found here for Ron Paul. and here for Tom Tancredo.
In a nutshell, Tancredo voted for both the measures that Paul did and either voted or consponsored several measures that would have decrease guest worker visas, but also in 2005 allegedly cosponsored H.R. 3938 which was according to the ABI going to:
"increase the annual cap on employment-based visas by 120,000 to a total of 260,000. In addition, it would double from 10,000 to 20,000 the number of legal, permanent, resident visas for unskilled workers."
Rob Sanchez had some additional criticisms of Tancredo's record.
Sanchez's Newsletter also had some rather sad quotes from Paul in a Lou Dobbs interview:
DOBBS: The idea that the United States, as Bill Tucker reported tonight, H1B visas being used under the rubric of bringing in bright foreign workers into this country, in point of fact, as our research has demonstrated, more than half of those for low-skilled jobs. What would be your position there?
PAUL: That I would not have as much concern about. But I think it needs monitoring. My big concern are the illegals, I'm concerned about all the enticements we give for the illegals, automatic citizenship by being born here. And then just be here for a while and you get in front of the line. Free medical care, free education. No wonder they bring their families. So I would get rid of all the benefits to the illegals and deal with that and the legal entry, then it needs more monitoring, and looking into these H1B and different categories that we have.
Now, I think both Paul and Tancredo are far more concerned about the issue of Guest worker Visas than Giuliani, Romney, McCain or Fred Thompson. I don't think their stands are perfect, but at the same time, they are operating in a situation where there is a real lack of credible economic analysis dealing with this topic. Sadly, much of what economic literature exists has been written by folks affiliated with interests like the Fed that have stake in looser immigration policy that has nothing to do with the welfare of the average American—or for that matter Mexican. Now are the stands of Tancredo or Paul good enough to do more than slow down damage? I doubt it. However, if Paul or Tancredo get enough votes to require a prime time speech during the Republican National Convention, that is still big news. If either of them do well enough in the early primaries and caucuses to threaten the big money candidates, that will also send a real signal and this year there is enough competition for the nomination, we just might see some of those candidates forced to at least think about immigration issues. The big money candidates have the kinds of resources to get some serious analysis done on this topic that is simply outside the reach of either Paul, Tancredo or the folks at the major immigration think tanks. What the big money candidates lack is motivation or a feeling that immigration is an important and political viable issue-and that is what Paul or Tancredo can change.