The fact is, that since the end of World War II, only one President, Ronald Reagan, was able to hand the reigns of his eight-year Presidency to another of the same political party: George H.W. Bush. I believe the only reason this happened was because Reagan was considered the best President since World War II and Americans wanted to give Republican leadership another chance.
But, other than George H.W. Bush's win, this is how the Presidency has cycled between Democrats and Republicans:
Harry S. Truman, a Democrat who served 8 years, was replaced by Republican Dwight Eisenhower. After Eisenhower's 8 years, John Kennedy (assassinated) and Lyndon Johnson -- both Democrats -- served 8 years and, were followed by Richard Nixon, a Republican. After 8 years of Nixon (resigning in shame) and Gerald Ford, Democrat Jimmy Carter then occupied the White House. Four years later the 12 years of Republicans Ronald Regan and George H. W. Bush were followed by Democrat Bill Clinton. Then, Clinton, after 8 years, was replaced by Republican George W. Bush; replaced 8 years later by Democrat President Barack Obama.
In total, since the end of World War II, 6 Republican and 6 Democrats have been presidents of this country. It appears that Americans can't take much more of one party or the other after 8 years. Not a glowing testament to one being better than the other.
So, for Hillary Clinton or any other Democrat hoping to be elected President in 2016, history is not on your side. Especially with Barack Obama having such low approval ratings and now being considered this country's worst President.
Wikipedia: List of Presidents Of The United States: http://en.wikipedia.org/wiki/List_of_Presidents_of_the_United_States
Obama worst president since WWII, new poll shows. Reagan the Best: http://www.washingtontimes.com/news/2014/jul/2/obama-worst-president-wwii-new-poll-shows/?page=all