1) Most of the country -- White or Black -- was behind FDR in 1936.
2) Most Blacks in large parts of the country couldn't vote then. If African-Americans had the vote across the country and had held office in states where they couldn't, those numbers might have been different.
3) FDR was personally popular with Blacks and won their votes, but it took time for African-Americans to fully embrace the Democratic Party. In FDR's time, African-Americans went from identifying strongly with Republicans to identifying 50% with the Republicans and 50% with the Democrats. It would be another 20 years before African-Americans registered overwhelmingly with the Democrats. Eisenhower and Nixon won over a third of the Black vote when they ran.
Conservative democrats switched fairly quickly.
It depends on what you mean by "fairly quickly." From when to when? Southerners who had complaints about FDR still voted for Stevenson, Kennedy, maybe Johnson, definitely Carter. That's not "fairly quickly" in my book. Things are even more unclear with the less liberal Northern Democrats, who might have swung to Nixon or Reagan, but who swung back in later elections (or died).
My point, though, was that people can come up with all kinds of theories why Jews vote Democrat, but it's very unlikely that they'd swing to McCain (in a very Democrat) year or Romney because of Obama's Muslim heritage or because he was liberal or progressive. If you've been a convinced liberal for decades, you aren't going to run away because of one candidate.
True, Jimmy Carter did do a lot to drive Jews away from the Democrats, but even though Obama may be as bad as Carter there are reasons why he has better control of his base -- White or Black.
The fact is that Jews have never voted republican, and it isn’t because of your bizarre claim about them being in La La land politically and just voting the same for a 150 years out of habit.
Actually you claimed that everyone takes forever to “change”, which just isn’t true at all.
You can’t ignore the facts about blacks for instance, until 1932, they always voted republican, in 1936 they made an instant, and permanent switch.
In 1932 the black vote being republican, gave the democrats the unsurprising 23%, and in 1936, they made the instant and permanent switch, suddenly going 71% democrat, and staying there.