Political polarization is spurring partisans to extremes, but there’s a simple change Congress could make to reverse this alarming trend: mandate that its members be elected by a majority of votes.

Americans probably think the law already requires this, given the Founders’ reverence for majority rule as an element of self-government. Yet all but six states permit plurality winners, meaning that federal lawmakers can be elected even if they do not secure more than 50 percent of the general election vote.

States are generally authorized to set their own voting rules. But requiring that a candidate win a majority in the general election is fully within Congress’s constitutional power. Article I, Section 4 empowers Congress to “at any time by Law make or alter” any “Regulations” concerning the “Manner of holding Elections for Senators and Representatives.”

Imposing this requirement would be healthy for democracy not only because, by definition, it would produce results that a majority of voters want — it would also help elect more moderates from both parties, officeholders predisposed to working across the aisle to legislate in the public interest.

Congress could make this change while being respectful of states’ roles as “laboratories of democracy,” because there are any number of ways to achieve majority rule. They could adopt a “top two” system like that in place in California and Washington, in which a nonpartisan primary sends two finalists to the November election.

They could experiment with “approval voting,” as St. Louis did for the first time in its mayoral election this week, which is similar to the “top two” system except that in the nonpartisan primary voters can support as many candidates as they want, rather than just one. Or they could adopt ranked-choice voting in the general election, preceded by either a nonpartisan or partisan primary, as in Alaska and Maine respectively.

Any of these options, and others also, permit a centrist candidate — like Sen. Lisa Murkowski (R-Alaska) or Sen. Susan Collins (R-Maine) — to prevail if, but only if, that’s what the electorate as a whole prefers.

To understand how pernicious the current dynamic is, consider the rare race in which a moderate candidate attempts to challenge the polarizing effect of the existing system. For that, we reach back a decade, because usually centrists don’t even try.

Florida’s 2010 Senate race featured three general election candidates: Republican Marco Rubio, who won 49 percent of the vote; then-Governor Charlie Crist, who was running as an independent after dropping out of the GOP primary and received 30 percent; and Democrat Kendrick Meek, who attracted just 20 percent. Had a majority been required, it’s possible that Crist would have picked up enough Democratic support to beat Rubio.

What’s worse: Electing plurality winners has the effect of deterring third-party candidacies like Crist’s in the first place, leaving the general election a contest between the two major-party nominees. If the parties choose more extreme candidates in their primaries — as is happening increasingly, especially on the Republican side — then the November winner will be a more polarizing politician.

Looking ahead to 2022, the problem of polarized outcomes contrary to majority preference is likely to intensify. In Ohio, for example, where moderate Republican Sen. Rob Portman is retiring, he is likely to be replaced by a far more conservative Republican who wins the GOP primary and may well defeat the Democrat in November. Ohio could be left with a polarizing extremist instead of a Portman-like traditionalist whom a majority of all the state’s November voters would prefer.

In a blue-leaning or purple state, Democrats can deter a GOP primary from veering too far right. But any red-leaning state is vulnerable to the same phenomenon as in Ohio, whether in 2022 or after.

There ought to be sixty senators willing to require majority winners: 10 GOP traditionalists wanting to save their own party from extremism, plus all 50 Democrats eager to help prevent their Republican counterparts from becoming the anti-democracy caucus.

The question of how and whether to apply this rule to House elections is slightly more complicated. As long as the House remains full of single-member districts, all the same reasons apply — if not more so, given how partisan gerrymandering combined with primaries maximizes polarization. But if Congress moves to multimember districts for the House, as some have proposed, the same rationale would not apply.

Congress already adopted a majority rule once, in 1866, for Senate elections, but that was before the 17th Amendment, when state legislatures still elected senators. It’s time to reinstate this rule — paving the way for a more functional Congress to consider additional reforms now stymied by entrenched partisan division.

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