It's 1979, and the Southern Baptist Convention isn't that terribly different from most mainstream Christian denominations: since the '50s, it's become increasingly liberal, embracing modern scholarship and social stances while moving away from Biblical inerrancy.
That summer, in Houston, everything changes. Fundamentalists, angered by what they see as repeated betrayals of the church's founding principles, bus in supporters. Instead of a genteel administrative process, they've treated the SBC apparatus the way a political machine does; organizing relentlessly with an eye to seizing as much power as possible.
It works. The moderates and liberals are routed in an "orchestration from the sky boxes." With their victory, the fundamentalists gain access to thousands of churches to spread their views, along with control over universities, media, built-in loyalty and a budget to use for whatever else they want to do. The SBC has remained conservative to this day, and the 1979 takeover played a major role in making the religious right-wing a political force. With the SBC in their grasp, fundamentalists had a foundation to back the efforts of previously scattered fringe groups.
It's 1896, and the Democratic Party is largely a conservative organization, dominated by the "Bourbon" wing and Southern aristocrats; there hasn't really been a major liberal faction of the party since the 1830s. President Grover Cleveland is such a perfect Gilded Age fat cat that Ayn Rand will later swoon over him.
But things are changing. The Populists have made gains throughout the Midwest, including voting friendlier Democrats into office on fusion tickets. While much of the rest of the party is divided, a young congressman, William Jennings Bryan, spends the year-and-a-half leading up to the convention getting to know the delegates and leading the populists to control the endless ground-level meetings that the party's elite assume will turn out in their favor. Instead, Bryan and his allies aimed, in his blunt words, to "organize and take charge of and control the policy" of the party. That summer, hundreds of new delegates pour into Chicago. "They are assembled now," Bryan thundered. "Not to discuss, not to debate, but to enter up the judgment rendered by the plain people of this country."
He rallies them with a hell of a speech and the left wing takes control of the Democratic institutions. The Dems don't take the presidency, but the populists still remake a major political party. While its power has waxed and waned, since 1896 the Democrats have always had to deal with a progressive faction in their midst. The Bourbons were furious — they considered the populists an illness — but the virus had already taken hold.
An institution is, at heart, just a name and a structure attached to resources. That's it, and it means that determined groups of people can infect them until they turn into something very different.