Donald Trump’s attack on Sen. Ted Cruz’s citizenship status is a losing strategy for Trump. What’s more, it demonstrates the intellectual bankruptcy of Trump’s policy-free campaign. The attack is damaging to both Trump’s own credibility and to the primary process itself.

Let’s start with the party process. Here’s what Trump said about the issue, after noting that Cruz was born in Canada – to an American mother: “Republicans are going to have to ask themselves the question: ‘Do we want a candidate who could be tied up in court for two years?’ That’d be a big problem. It’d be a very precarious one for Republicans because he’d be running and the courts may take a long time to make a decision. You don’t want to be running and have that kind of thing over your head.”

In other forums, he has more specifically said Democrats would be quick to challenge Cruz’s citizenship in court.

Here’s what’s wrong with that. Since when does the GOP give Democratic lawyers a say in who wins the Republican nomination?

Of course, Democrats would sue. Based on a reading of the Constitution and the case law, they would lose. But their threat to file a lawsuit should have no bearing on how the Republicans conduct their primary.

Giving Democratic lawyers a veto over a primary candidate is a terrible precedent. They could later use that to their advantage in pretty much any lineup of a general election. Because the Constitution itself is vague about citizenship (though the case law is less so), they could challenge whether Sen. Marco Rubio is “natural-born” because his parents were immigrants. Donald Trump’s mother was Scottish.

The point here isn’t the merit of their lawsuits – it’s the inevitability. They will sue, but so what?

The Republican presidential nominee should be chosen by Republican voters – not Democratic attorneys, and certainly not by the mere threat of a Democratic lawsuit.

Second, the citizenship attack on Cruz shows how few substantive arguments Donald Trump is making in this primary process.

Trump has taken some heat for flip-flopping on many, many positions. His argument that Ronald Reagan changed his mind has some merit. But the policy problem that Trump has is not just that he’s been inconsistent, it’s that he has no real policy answers to offer.

When pressed about how he would replace the Affordable Care Act, he said simply, “with something terrific.” He gets his foreign policy information and views “from the shows” on Sunday morning.

His views on many issues lean toward populist – but insubstantial. He wants a 45 percent tariff on goods made in China, with no thought to the trade war that would follow, much less to the hit consumers would take in this country as everything we buy goes up in price.

He tried to make nice with evangelicals at Liberty University, but he doesn’t even speak the language.

For his part, Cruz has many positions laid out in great detail – providing any serious opponent with a target-rich environment for policy disagreements.

But Trump hasn’t gone there – because he can’t.