Who should be represented in our elections? That’s the question at the heart of Democratic opposition to the Trump administration’s decision to add a question about citizenship to the Census, a case now before the Supreme Court.

It’s also at the heart of Bernie Sanders’ proposal that incarcerated felons be given the right to vote.

That leading Democrats are now seriously opposed to the Census inquiring into citizenship, and at the same time favor giving felons the right to vote, is a sign of how far we have fallen from the idea that voting in our elections is one of the most sacred privileges Americans enjoy.

Only citizens can vote, and that’s what’s behind the Supreme Court case. At issue there is whether the Census form can ask whether a person is a citizen.

But Democrats argue that asking about citizenship will discourage immigrants, particularly Hispanics, from answering the Census and thus result in such groups being undercounted. So far, lower courts have accepted this bizarre argument, though the Supreme Court justices are likely to overturn their holding, likely on the ground that Congress has left it up to the executive branch to design the Census, period.

If someone isn’t a citizen, he shouldn’t count when congressional-district boundary lines are drawn up. Otherwise, non-citizens will be overrepresented in Congress. If there were a district where only half the residents are citizens, it shouldn’t have full representation in the House of Representatives.

What liberals are playing with is one of the most important things about belonging to a country — the sense of fellow-feeling for fellow citizens.

Americans are willing to be taxed to pay for health care for people who can’t afford it, because they’re fellow citizens. It doesn’t matter what their race or religion is. Citizenship trumps all that. But take citizenship away, and everything changes. I might think that Croatians are great people, but I don’t owe a thing to the Croatian health-care system.

The leftist who wants a good health-care system, and who tells us to ignore whether someone is a fellow American, is seriously confused. If he hates nationalism and citizenship, he will be throwing away the best argument for a decent social safety net.

So does every citizen get a right to vote? No, people in prison don’t get to enjoy that privilege. Most states don’t let felons who have been released from jail to vote, either, though that is beginning to change in some states.

The question is whether you lose some of the privileges of citizenship by your criminal behavior. In France, that loss is called “civil death.”

But being in jail is different. Like citizenship, that isn’t about race or religion. It’s about being found guilty of a serious offense.

If you are in prison, you’re subject to the worst punishment most states can inflict one anyone. Barring your voting rights is no greater burden and is justified if the prisoner has been found to be so unworthy as to merit prison time in the first place.

I don’t know what the best set of criminal laws might be, and I don’t know who my local prosecutor is. I don’t think I have voted in city elections about who should be my sheriff. I can’t vote wisely about that, so I don’t.

But I don’t think people in prison should even have the right to vote on things like that. I don’t think they would have the best interests of the community in mind. The criminal shouldn’t be able to vote for his prosecutor. We don’t need his advice on what’s a crime.

The argument for giving felons voting rights when they have been released from prison is different. Released prisoners have paid their penalty, it’s said. Let them have a fresh start. But if someone is still in jail he hasn’t paid his penalty. He is still paying it.

But that doesn’t wash with Sanders and other Democrats, and they take the argument to its logical conclusion. They would give voting right to Dzhokhar Tsarnaev, the Boston Marathon bomber. The people he and his brother killed lost their lives and their voting rights, and is he now to vote in their place?

Voting is one of the cherished rights of American citizens. Let’s not cheapen it or our democracy by treating it as a matter of no importance.

Felons aren’t permitted to own guns, because we rather suspect they wouldn’t be putting them to good use. The same can be said for their voting rights.

F.H. Buckley teaches at the Scalia Law School at George Mason University and is the author of “The Republican Workers Party: How the Trump Victory Drove Everyone Crazy, and Why It Was Just What We Needed.”