When did blacks start voting for Democrats almost exclusively?

Although there are black Republicans, Libertarians and black Tea Party members, until the mid 1930s with the 1936 re-election of Franklin Roosevelt, black Americans had always voted for Republicans--the party that freed them after the Civil War, the party that allowed them representatives in the House and Senate.  Democrats were the party of the KKK, Jim Crow and lynching. Democrats took their guns.   FDR did nothing for blacks to stop those terrible injustices, but he did provide them the same aid during the Great Depression that whites got.  Like public works programs at Howard University. That was huge!  By then many blacks had fled to the northern cities to find work. 

Although FDR did nothing to stop the crimes going on in his party, it was enough to win over blacks increasingly to Democrats in the north.  In the south blacks still couldn't register as a Democrat  which is why Martin Luther King, Jr. and Condi Rice’s father were Republicans.  The civil rights bills of the last century were proposed by Republicans, with little support from Democrats. Republicans even tried to pass an anti-lynching laws.   Between 1882-1968 nearly 200 anti-lynching bills were introduced in Congress, and three passed the House.  Seven presidents between 1890 and 1952 petitioned Congress to pass a federal law. Democrats defeated them. The 1964 Civil Rights Act would not have passed without support from Republicans.

Senator Strom Thurmond (D-SC): "This so-called Civil Rights Proposals, which the President has sent to Capitol Hill for enactment into law, are unconstitutional, unnecessary, unwise and extend beyond the realm of reason. This is the worst civil-rights package ever presented to the Congress and is reminiscent of the  Reconstruction proposals and actions of the  radical Republican Congress."

But has the Democratic party really changed?  Today, abortion is supported by Democratic Party Platform.  Abortion ends about 40% of black pregnancies (57% in New York City).  Margaret Sanger, the founder of Planned Parenthood, of which Obama is a huge supporter, favored eugenics and eliminating black babies.  Blacks don’t seem to know their history with the Democrats.