A common belief among political analysts is that someone running for his or her party's nomination for president of the United States must choose a different strategy once the nomination is secured. To be nominated, the candidate must appeal to voters from one party - Democrat or Republican - but in a general election a party's nominee must appeal to voters from both parties as well as independent voters. Which of the following offers the best explanation for this change in strategy?

A) the Arrow Impossibility theorem
B) the voting paradox
C) the median voter theorem
D) rent seeking

First, we suppose that voters are normally distributed, in this case each tail represents either democrats or republicans. The median voter theorem states that: if candidates remain only with their party ideals, which means that they only represent extreme ideas (either republican or democrat), candidates would only receive votes from people near each tail (not shaded part of the graph). And they would lose people that are not fully represented by only one party that are located at the middle of the graph: they are called median voters (shaded area). That is why candidates try to approach the other party or seem independent, because they are trying to gain more voters that are not represented by extremes. For example: if the democrat candidate approach to republican ideas, then he or she would gain voters on the blue shaded area and if the republican candidate approach to the democrat ideas, then he or she would gain voters on the orange shaded area. THE GRAPH IS ATTACHED