Republicans should have adopted Democrats' primary rules -- and vice versa

As for Republicans, Donald Trump is the kind of disruptive candidate more common among Democrats — deeply unacceptable to many party voters and officeholders.

But Republican rules have enabled him to amass a big delegate lead by winning pluralities of the vote in multi-candidate fields. Under Democratic proportional representation rules, according to the estimate of proprietor Nate Silver, Trump would have won nearly 100 fewer delegates in contests up to March 6.

And that was before the first winner-take-all primaries March 15. By my back-of-the-envelope estimate, proportional representation rules (allocating delegates only to candidates meeting a 20 percent threshold) would have cost Trump a little more than 100 delegates net in post-March 6 contests.

So under Democratic rules, instead of being about 240 delegates short of the 1,237 needed for the nomination as he is now, Trump would be about 440 delegates short. In that scenario he would have to win more than 60 percent of remaining delegates, almost surely impossible for a candidate who has won just 40 percent so far. It’s the same position Bernie Sanders finds himself in.