First, it’s important to understand that foreign policy isn’t his primary focus: He’s economically liberal, in the classical sense, and economic issues make up the bulk of his political message. His stump speech, the one that references Rawls, is a call for the GOP to recast its small-government stance to emphasize what he’s calling “opportunity conservatism” — the belief that conservatives “should conceptualize and should articulate every domestic policy with a laser focus on easing the means of ascent,” as he put it in a January speech in Austin.

Beyond economics, his approach is a bit more idiosyncratic. He’s ideological, even compulsive, with regard to the Constitution. This is a longstanding preoccupation — as an undergraduate at Princeton, he wrote his thesis on the 9th and 10th amendments — and apparently a sincere one. It helps explain why he gave his colleague Rand Paul a much-needed break during his March 6 anti-drone filibuster. He’s firmly against gun control, but that stance is rooted in his reading of the Constitution rather than any affinity for gun culture. (Cruz, more nerd than sportsman, would look no more plausible skeet shooting than Barack Obama.)

It also helps explain Cruz’s stance on immigration. Many observers were surprised when Cruz conspicuously declined to make common cause earlier this year with Sen. Marco Rubio on immigration reform. Cruz, like Rubio, is the son of an immigrant from Cuba, and Texas Republicans have, as a group, been more moderate on the issue than the national GOP. But unauthorized immigration is, of course, both an economic issue and a legal one. Someone like Texas Gov. Rick Perry, who signed Texas’s 2001 law that made certain undocumented students eligible for in-state tuition at the state’s public colleges and universities, is looking at it through the former lens. Cruz sees it as a rule-of-law issue, arguing that establishing a path to citizenship would be “profoundly unfair” to legal immigrants.