Marc A. Thiessen writes:

With three polls showing her in the lead, Sen. Elizabeth Warren (D-Mass.) may soon eclipse former vice president Joe Biden as the front-runner for the Democratic presidential nomination. That’s great news for Republicans, because Warren has a problem: The central message of her campaign is that the economy is working for the very wealthy but it is not working for ordinary Americans. Unfortunately for her, ordinary Americans disagree.

That is great news for Republicans. But that doesn’t mean it’s great news for people who support Republicans because they don’t like left-wing economic policies. In fact it’s bad news for them.

And the reason has to do with the median voter theorem. Here’s what William F. Shughart II writes in “Public Choice,” in David R. Henderson, ed., The Concise Encyclopedia of Economics:

Studying collective decision-making by committees, Duncan Black deduced what has since been called the median-voter theorem. If voters are fully informed, if their preferred outcomes can be arrayed along one dimension (e.g., left to right), if each voter has a single most-preferred outcome, and if decisions are made by simple majority rule, then the median voter will be decisive. Any proposal to the left or right of that point will be defeated by one that is closer to the median voter’s preferred outcome. Because extreme proposals lose to centrist proposals, candidates and parties in a two-party system will move to the center, and, as a result, their platforms and campaign promises will differ only slightly. Reversing 1964 presidential hopeful Barry Goldwater’s catchphrase, majority-rule elections will present voters with an echo, not a choice. If the foregoing assumptions hold, the median voter’s preferences also will determine the results of popular referenda. As a matter of fact, anticipating that immoderate proposals will be defeated, the designers of ballot initiatives will strive to adopt centrist language, in theory moving policy outcomes closer to the median voter’s ideal point than might be expected if decisions are instead made by politically self-interested representatives.

Those 4 assumptions are quite strong and unlikely to hold up in the real world. But that doesn’t mean the median voter theorem is useless. It still has power in explaining two things: why candidates’ platforms in a general election, when 2 parties contend, will often be similar. Think of Nixon and Humphrey in 1968: that’s the first presidential election I followed somewhat closely. I remember pundits referring to them as Tweedledum and Tweedledee. (Some wags at the time referred to them as Tweedledum and Tweedledumber.) There wasn’t a huge difference between the policy positions they articulated (with one important exception: Nixon promised to end the draft.)

Or think about what happened in the Goldwater/Johnson election. Vietnam was a big issue, as the war was just getting going. Goldwater took an extreme position in favor of the war. Did Johnson go all dove? No. He was pro-war also, but less extreme. That led to the old joke that might have actually been based on an actual voter’s comment: “I was told that if I voted for Goldwater, we’d bomb North Vietnam. So I voted for Goldwater and sure enough we bombed North Vietnam.” And LBJ won with about 60% of the vote.

If a politician wants mainly to win, and if his opponent takes positions that are far from the median voter’s view, his best strategy is not to take the same views but to move towards that view. He wants to motivate his base to show up at the polls and so he’s unwise to go all the way to the opponent’s views, but he will go some of the way.

So in this case, with Elizabeth Warren being so far left, if she wins the nomination Donald Trump’s best strategy is to move further left than he would have if he had run against a more-moderate Democratic candidate. So it wouldn’t be surprising to see Trump advocate, say, a $10 or $12 an hour minimum wage, to take just one example.

The only exception would be if the politician is highly principled and if his main goal is to implement particular policies rather than to win. Does that sound like Donald Trump to you?

By the way, I posted about this 2 years ago.