In the following Washington Post's article (Feb. 13) reporting the outcome of CPAC 2011, I found the phrase *if you must know*.

I think this phrase means *though it may not be essential knowledge that you are supposed to have*, or *just for your reference*. What is the difference of nuance among *if you must know*, *you may know*, and *you might know*, which is difficult for non-native English learner to discern?

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> The three-day Conservative Political Action Conference ended Saturday afternoon with a meaningless presidential straw poll (if you must know, libertarian gadfly Ron Paul won for the second year in a row). 
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