The new deal democratic coalition emerged in part when

The correct answer is when African Americans ended their historic ties with the Republican Party

That is because during the Civil war it was the Republicans who fought for abolition of slavery and Democrats who wanted to keep having it. This made African-American voters natural supporters of the republican party for decades to come, but this ended during FDR when the democratic block managed to pull them to their side.

The statistics for the eastern war are grim. more than three-million men died in the fighting, more than nine-million men were wounded, and every major country which participated lost its form of government.