Emmanuel Macron has completed a political revolution. The man swept out of nowhere, with no party behind him, and in a few short months, managed to secure the French presidency, then lead his new movement to a substantial legislative majority. Now he’s proposing to embark on another revolution by reshaping the legislature: to reduce the number of representatives, to limit lawmakers’ terms, and to provide “a dose” of proportional representation.

These are all proposals that get floated in the U.S. as well. And it’s easy to see why.

Why reduce the size of the legislature? Because the larger a deliberative body is, the harder it is to get enough members to agree on anything. Three people may debate where to have lunch, but in a group of 20, the issue needs to be settled by executive decision.

Meanwhile, term limits and proportional representation — the idea that a party should be represented in government in approximately the share that it received of the national vote — promise to fix everything people hate about America’s political inheritance from England: Single-member districts elected on a first-past-the-post system tend to squash smaller parties, resulting in two megaparties that seem to please no one fully. You end up with parties full of entrenched, self-dealing legislators who cling to their seats for decades, thanks to a combination of gerrymandering and voter bias towards the devil they know.

All these ideas are, in fact, favorites of exactly the class of people that Macron represents and typifies: educated cosmopolitans of a technocratic bent, who think that most important problems can be solved by twiddling the system’s rules. They look at the messes created by the elderly political apparatus and think “We must be able to do better.” And when you look at those messes, it’s hard not to agree.

And yet, there are ample reasons to dislike what Macron proposes to do. Start with proportional representation, an idea that seems hard to disparage: popular parties should hold more power. Who could possibly disagree with such an obvious principle?

Well, maybe someone who’d looked at actual governments that use this system. Proportional representation makes it very hard for a party to get a majority. This often leads to unstable coalitions that have difficulty holding together or getting anything done. In the most extreme case, as happened in Belgium, no governing coalition can form, and the country is left without a government.

The instability of proportional representation can make the government hostage to tiny coalition members — which is why, for example, the ultra-orthodox parties have such outsize influence in Israel. This may be of particular concern to liberals, because France’s current system awards the far-right Front National only a handful of seats — behind even the moribund communist party — in a country where the nationalists recently took a third of the vote. If French politicians try to shun the National Front, as has happened in other countries, the coalition politics would be unstable indeed.

Smaller legislatures, meanwhile, may be easier to corral into action, but by the same token, they are less accountable to voters, because each legislator represents more of them. That means legislators have less time to listen to individual constituents, and significant interests may get lost entirely.

Okay, but what about term limits? Who wants political lifers fondly patting each other on the back while trading favors and entrenching their own power? Shouldn’t we all crave a body of citizen-legislators, bringing real-world experience into government, and then returning to some productive labor?

If we were all sitting around designing some theoretical system from first principles, for an imaginary country full of industrious yeoman farmers, I would probably find myself enthusiastically endorsing this idea. But sadly, the real world, as so often happens, has declined to cooperate with our happy imaginations. When we get a look at term limits in practice rather than theory, they look a lot less attractive.

The citizen-legislator is a marvelous principle for a tiny, 19th-century government that practically doesn’t do anything at all. And if you have a viable plan for getting us to such a government, well, I’m all ears. But we in the Western democracies have 21st-century governments, whales so bloated that they have an entire ecosystem swimming along with them. As so happens with complex ecosystems, seemingly simple changes can have unexpected, even catastrophic effects.

For what happens when our citizen-legislators arrive in the seat of government, ideals clutched firmly in hand and just a short time to Make a Difference? They discover that the circling sharks (lobbyists, bureaucrats, etc.), unlike them, are not term-limited.

These lifers often have intentions just as noble as the citizen-legislators of our imaginations. But each of them is laser-focused on one priority. Their predation in pursuit of their priorities is limited mainly by their fear of legislators, and by extension, of the voters.

So while lobbyists and bureaucrats may be tempted to treat legislators like the proverbial mushroom — keep them in the dark and feed them manure — they can go only so far, because they know that next term, the legislator will probably be around, and will remember. Over time a few legislators gain expertise in a their subject areas, and can push back.

Term limits change that calculation. The citizen-legislators and their staffs arrive in Washington ignorant not just of the complexities of individual policy areas, but also of the ecosystem. By the time they know enough to recognize a shark and its agenda, they are getting close to their term limit, and their ability to threaten retaliation is waning.

So while it’s true that term limits strip power from self-interested politicians, that power is not returned to the voters. Instead it’s handed over to bureaucracies and interest groups — every bit as self-interested and self-dealing, but much less accountable to the public.

So why is Macron pursuing these changes? Because some of that power stripped from legislatures ends up empowering the executive. In a system like France’s, with a strong presidency, a weak legislature means a president with more scope for action.

I don’t say that he is acting from bad motives, mind you. Macron probably feels, with some justification, that reforming France’s often dysfunctional political economy will be impossible with the current legislature structure. Legislatures are, after all, the body most responsive and accountable to voters, and the reason that reforms have not happened before now is that each bad regulation or poorly designed welfare benefit comes attached to a group of voters with a powerful interest in continuing it — and they have the ear of some politicians.

And of course no political system ever designed is without problems. Israel may look enviously at nations with decisive elections, while we look enviously at those who get to have more than two parties. Who’s to say which problem is worse?

But those considering endorsing Macron’s program should give the question careful thought. As recent American experience has shown, “good government” often isn’t — and the devil you know really may be better than the beckoning stranger.

Bloomberg