From yesterday's Huffington Post:
"Our founders intended for [the judicial branch] to be the least consequential of the three branches of government," said Santorum. "How do I know that for a fact? Because it's Article III. Article I is Congress, Article II is the president and Article III is the courts. If it was the most important, they wouldn't have put it third."
It's not impossible that Santorum was joking about this - I couldn't find a clip to evaluate - but if so the report doesn't mention it. It does mention that he "elicited laughter" with another comment (about making a new court in Guam and sending all the Ninth Circuit judges there), but as far as I can tell, he was serious about this one.
Lots of arguments have been made about the relative power of the three branches, but I don't think "we get mentioned earlier" has been one of them. You could certainly argue that the legislative branch is the most important, because (in theory) it makes law that the other two only enforce or interpret. Alexander Hamilton called the judiciary "the weakest of the three departments," but again, that's because it doesn't have real power to enforce its decisions, not because it only shows up third in the table of contents. And since the executive seems to be able to start wars on its own and blow up or detain U.S. citizens if it wants to, those seem like pretty good arguments that it's not currently in second place. So all in all, this argument of Santorum's appears to suck.
To be fair, I did find one authority that seems to argue along these lines:
The judiciary is often called the third branch of government. Why, you might ask, if it's so important, does the Court come in last in the American tri-partite system? In part, this designation is the result of the federal court system having been outlined in Article III of the Constitution. (Article I concerns the legislature, and Article II addresses the executive branch.) But Article III is also remarkably short and makes the judicial branch seem almost like an afterthought.
Source: U.S. Constitution for Dummies.
Santorum went on to note that the Constitution actually only creates the Supreme Court, with "inferior courts" to be created, uncreated, or sent to Guam as Congress sees fit. That one's valid (Art. III, sec. 1), although Santorum's ideas for getting around the fact that Article III judges hold office for life are another story. Hamilton's ultimate point was that "[t]he complete independence of the courts of justice is peculiarly essential in a limited Constitution," precisely because that branch is otherwise so weak. Santorum's approach (and Gingrich's) ignores that.
Granted, Hamilton might have been better off had he not skipped dueling practice to write that Federalist Paper, but we're lucky he did. It's a good one.