Unconditional, rabid support for Israel has been a stock Republican policy since around the 1980s. Democrats have been bullied into kinda-sorta going along with it by the sheer savagery of the conservative support.
And a lot of very bright, very skeptical, very fact-oriented, very conspiracy-theory-debunking people (such as your humble narrator) have wondered about that: why conservatives–traditionally not huge fans of Jews (and especially Jews with no oil)–would suddenly get so FIERCE about supporting Israel. And many of us have come to an uncomfortable conclusion.
During that time (the 1980s), ultra-conservative fundie Christians were quietly worming their way into that halls of power. Especially troubling was that a fair number of these people were actual end-timers, people who believe that we are literally in the End Times predicted in Revelations, and that Jesus is due back just any day now.
But there are rules. Before all this can happen, certain other things have to happen. And one of those things–essentially–is that the Jews have to be in control of Jerusalem.
The Republicans excel at putting up a unified public front on party policy (well, other than during primary season…), but behind the scenes, they fight vicious, bitter steel cage death matches with each other over policy and power. But once the matter is decided, it becomes Official Party Dogma, and everybody gets in line, even if they don’t know why.
And this is what many people who have studied the matter conclude happened: some end-timers fought and won a behind-the-scenes deathmatch, and absolutely unconditional support of Israel became policy. Of course, they didn’t send out a memo saying “we support Israel unconditionally because Jesus is due back,” they just said “we support Israel unconditionally.” And appended a list of approved talking points that don’t actually explain anything. They typically offer up lame excuses like “Israel is a key strategic ally.” Well so is England, but when was the last time you saw a conservative flip their shit because somebody dissed the Queen? Or, “it’s the only democracy in the region.” Yuh huh. And when were Republicans suddenly fans of democracy? They have supported to overthrow of more than one democratically-elected government in favor of a murderous dictator. That dog don’t hunt.
There is very little hard evidence for any of this (the invasion of the government by ultra-conservative Christians is well-documented, go read up on The Fellowship for just one example). But all the searching one can do for an alternate explanation–one that actually holds water–has turned up zilch.