The result turned out to be an unbeatable combination: virtually universal support from black voters, who turned out as strongly as in 2008, plus decisive backing from members of the younger and fast-growing Latino and Asian American communities, who chose Obama over Romney by ratios of roughly 3 to 1. All of those groups contributed to Obama's majority among women. (Gay voters, a far smaller group, went for Obama by a 54-point margin .)
Here I'll help.
If 54% (your interpretation) voted for Obama, then 46 voted for somebody else. 54-46 =8.
But instead the difference "the margin" is 54. X - Y = 54. X + Y = 100.
X = 54 + Y.
54 + 2Y = 100.
2Y = 46.
Y = 23.
X = 77.