Question: From Obama's second inaugural speech:

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> We, the people, declare today that the most evident of truths – that all of us are created equal – is the star that guides us still; just as it guided our forebears through Seneca Falls, and Selma, and Stonewall; just as it guided all those men and women, sung and unsung, who left footprints along this great Mall, to hear a preacher say that we cannot walk alone; to hear **a King** proclaim that our individual freedom is inextricably bound to the freedom of every soul on Earth.
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I know that he was referring to Martin Luther King, Jr. But why did he use the indefinite article "a" before "King"? Is it better, for example, to use "Dr. King" or just "King" instead? Does the use of the word "a King" provide a sense that Dr. King was the king of something, such as righteousness, justice, etc?

Answer: 
By adding the *a*, Obama elevated MLK to an archetype, just as an intellectually average or above person might say, "I'm no [= not **an**] Einstein, but it seems to me that doing the same thing and expecting a different outcome is insanity in this case". It doesn't mean that MLK was the king of anything, only that he is a symbol.
It is a pun being used stylistically. MLK is likened unto a king, and King happens to be his name.