Even as most everyone continues to say the Trump thing is a summer diversion or a fire sure to burn itself out, or a stalking horse for somebody or other, what’s usually missing is an exact scenario of how the man will bow out. After all, he’s got the money and celebrity to go the distance and perhaps a bit further (into the general election!). He’d have to be pretty damn dead for the cameras to go away to cover Marco Rubio’s policy speeches, right?

But at Ten Miles Square today, Steve Waldman raises another issue: thanks to Super-PACs, the winnowing of the field we would normally count on to enable somebody to dwarf Trump’s poll numbers–and eventually to croak him in a one-on-one competition–may not happen for a very long time.

In a way, this is a throwback to an earlier time when fractional candidates could win the nomination. In 1972, George McGovern won the Democratic party nomination with a total of 25 percent of the primary votes, in part because several candidates were strong enough to remain appealing until the convention: Hubert Humphrey with 25 percent; George Wallace, 23 percent; and Ed Muskie, 12 percent.

In some of the state contests, the presence of several strong contenders ended up helping McGovern. For instance, he won the April 4th Wisconsin primary with 29.5 percent of the vote as Wallace got 22 percent, Humphrey go 21 percent, Muskie got 10 percent, Scoop Jackson got 7.8 percent and John Lindsay (!) got 6.7 percent. McGovern benefited from those other candidates maintaining strength deep into the primary season. Trump will, too.

Now there were some special circumstances in that 1972 contest. For one thing, winner-take-all primaries were still allowed by Democrats then, and McGovern’s victory in California pretty much sealed the deal (indeed, the ABM–Anybody But McGovern–effort at the convention revolved around an unsuccessful effort to demand the proportional rewarding of delegates. True, Republicans do maintain a winner-take-all option for states holding primaries after March 14, but so far the only state moving towards that system is Florida, where you’d have to think Jeb Bush or Marco Rubio would have an advantage.

But Steve’s right: the longer the field stays big the longer Trump can stay in, and crazy things could happen next spring. That’s part of the price Republicans will pay for insisting on a Wild West nominating system where money walks tall.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.