Over at The American Conservative, I made the argument this week that all things considered, it’s probably best for Republicans up and down the party to get behind Donald Trump.

I didn’t make the argument because I think Trump is the best candidate. I made it because getting behind him makes the most strategic sense. He has the lead in the delegate count. Most Republicans, 58 percent according to an AP poll released this week, say the delegate leader should get the nomination whether or not he has exceeded the threshold of delegates.

But there’s another issue that’s only now getting the attention it deserves. Party unity matters. Drew DeSilver at the Pew Research Center compiled the history of conventions in years in which the parties broke along factional lines. The grim takeaway this year for the GOP: Parties usually lose without unity.

Since the Civil War there have been eight Republican and 10 Democratic conventions that took more than one ballot to pick a nominee. In only seven of those 18 instances did the first-ballot leader win the nomination.

So with Trump, the Republicans might lose the general election. But without him, winning gets close to an impossibility.

DeSilver defines disunity as a candidate’s inability to win on the first ballot. The last time that happened was 1952 when Harry Truman persuaded Estes Kefauver to drop out so Adlai Stevenson of Illinois could run against General Eisenhower. But I’d make the case that unity matters beyond the convention.

The parties tend to realign every 40 years or so. When they do, one party enjoys more unity than the other. Beginning around 1954, when the Supreme Court struck down “separate but equate,” to around 1972, when George McGovern was dealt a crushing loss by Richard Nixon, the parties realigned.

Some Republicans became Democrats but many more Democrats became Republicans. From then, the Democrats were relatively weak and the Republicans relatively strong. With the exception of 1976, after Watergate, and 1992, after H. Ross Perot’s failed bid, the GOP was more or less united–and they won. (I’m leaving out 2000; that was decided by the Supreme Court.)

2008 saw the beginning of the Democrats’ turn at unity. No one knows what the future holds, but it is nevertheless abundantly evident, despite Bernie Sanders populist insurrection, that the Democrats haven’t been this unified since perhaps 1964.

The Republicans, however, may be entering a long period of fracture in which the white working class and even evangelical conservatives reassess their commitments to the party.

History doesn’t repeat itself, but it does echo.

Unity continues to matters, and the Republicans don’t have it.

John Stoehr

Follow John on Twitter @johnastoehr . John Stoehr is a Washington Monthly contributing writer. This piece originally appeared in The Editorial Board.