Sen. Ted Cruz (R-Tex.) waits during a commercial break in the first GOP presidential debate Thursday. (Chip Somodevilla/Getty Images)

Presidential candidate Sen. Ted Cruz (R-Tex.), made a series of promises at the end of last week’s GOP debate about what he would do as president.

“If I’m elected president, let me tell you about my first day in office,” Cruz said. “The first thing I plan to do is to rescind every illegal and unconstitutional action taken by Barack Obama.”

Okay. Pretty standard so far.

“The next thing I intend to do,” he continued, “is instruct the Department of Justice to open an investigation into these videos and prosecute Planned Parenthood for any criminal violations.”

[Planned Parenthood on offense, warns GOP against shutting down government]

Now, that seemed a bit odd. Seemed to have a whiff of a reverse Watergate about it. Or maybe it recalled that famous 2004 scene when Bush White House officials raced (unsuccessfully) to beat Justice Department lawyers to a hospital to get Attorney General John Ashcroft, in intensive care, to reauthorize Bush’s domestic surveillance program after the department determined it was illegal?

But Cruz is a lawyer. Even more, he was a clerk to the late Chief Justice William H. Rehnquist and solicitor general of Texas.

So we checked with some former top lawyers in the Bush and Obama administrations to get their views on Cruz’s promised move. They wanted to be on deep background (something about still practicing law).

“I am not sure there is any written protocol or policy,” one of them said, “but I am certain that there is at least a strong and well-respected practice that the President and the White House do not order up criminal investigations. At most, a president, through, for example, the White House Counsel, might express concern about a particular subject matter that could merit inquiry or more intense attention.”

Another lawyer agreed: “That was an odd thing for [Cruz] to say. The Justice Department is not like other institutions. The president can establish priorities of criminal prosecutions in general, but singling out an individual subject for prosecution” especially one you’ve campaign against and raised money about, “could create legal problems” and run counter to a “settled practice of self-restraint.”

It appears the president’s role in the post-Watergate era is seen as setting general law enforcement policies — for example, worry less about random pot smokers, more about corporate malefactors — than directing specific enforcement activities.

Well, Cruz is used to starting political firestorms …