Relevant history from 1968?

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4. Rejecting the sitting president is a recipe for the opposition party winning

Only twice has a party rejected its incumbent president for renomination and held the presidency: Buchanan and Garfield. Only Garfield was after the civil war with the entrenched two-party system.

And in both cases, the replacement had run a popular primary campaign.

It's really hard to convince the general population to vote for the status quo after the incumbent party rejects the status quo.