Donald Trump had a complete meltdown Thursday night when he got locked in this exchange with Marco Rubio over health care. Rubio kept pressing him on what his plan for health care was, and Trump responded by incoherently talking about getting rid of "the lines around the states." Essentially, Trump wants to increase competition by allowing insurers to sell plans across state lines without regard to the states's own insurance regulations. Rubio then noted that Trump was repeating this one idea over and over, to great applause. Then asked by CNN's Dana Bash if Trump had any more health plan specifics and if he wanted to add anything beyond obliterating "the lines," Trump's response was "No! What's to add?"

Setting aside the fact that Trump's understanding of health care policy is woefully inadequate, his one idea on health care isn't even a good one. Granted, this is an idea a lot of Republicans have floated and, in theory, increased insurance competition is needed and state insurance regulations are often an impediment to this. But in practice, the idea runs into the buzzsaw of federalism.

Outside of the hardest of hardcore libertarians, it's pretty safe to say Americans would be horrified the idea that the insurance industry would be totally unregulated. So if you want insurance sold across state lines without being subject to 50 different regulatory regimes to increase competition, somebody -- likely the federal government -- would have to still regulate the industry to protect consumers.

Would a one-size fits all approach to regulating the insurance industry be better? Again, in theory it could be. But in practice, that's highly unlikely. Even if Congress came up with a national regulatory framework, demagoguing insurance companies is second nature in Washington. The political compromise necessary to enact such a system would probably mean that even if Congress cut things down to size in states that have onerous insurance regulations, they'd also probably end up imposing more regulations on states where things are already more relaxed.

An even more likely scenario is that Congress uniformly makes everything worse for everybody. One idea to allow for more insurance competition would be for the federal government to set up some sort of health insurance "exchange" where consumers could buy insurance directly from competing consumers … Sound familiar?

That's because I just described Obamacare. Now the Obamacare exchanges are still basically run through the states, but the law would have been a good opportunity to leverage federal influence to cut egregious state regulations down to size. Instead, Democrats in Congress imposed so many new and poorly though-out regulations and coverage requirements on insurers participating in exchanges that Obamacare coverage has become ludicrously expensive. A typical Obamacare insurance plan -- one that costs $500 a month where and you have to pay $5,000 out of pocket before you see a penny in benefits -- isn't going to do much at all to help most Americans.

Consequently, the Obamacare insurance exchanges are going so poorly that, earlier this month, the Department of Health and Human Services brazenly and quite illegally took $3.5 billion in funds that were supposed to be returned to taxpayers and is using it to bail out insurers participating in Obamacare. That's because they're losing money hand over fist. Excess Obamacare regulations have forced them to try and sell a product on the exchanges that no one wants to buy. (Indeed, Obamacare enrollment is 40 percent below what was predicted.)

Now looking at ways to increase insurance competition between states is still probably worth examining, and some states have flirted with interstate insurance compacts and other potential solutions. But as Forbes editor and health care uber-wonk Avik Roy notes, enacting the idea is way more complicated than it seems.

Further, if this is your only idea for fixing health care, well, that's pretty pathetic. Or as Donald Trump might say: "Sad!" I haven't even touched on how Ted Cruz quite effectively skewered Trump last night for supporting Obamacare's individual mandate or his praise of socialized medicine. Further, it's worth noting that the guy in Congress who is arguably the most responsible for passing a law making it illegal for the Obama administration rob taxpayers of billions to bail out the insurers being strong-armed into enabling their stupid, unworkable exchange money pits was… Marco Rubio.

The point is, if you hate Obamacare and want to see it repealed, voting for Trump would be a really bad idea. It's plenty obvious he doesn't begin to understand the law or how to fix health care.