The midterm elections of 2014 have had the effect of creating a short term weakening of many potential Democratic Presidential nominees.
Hillary Clinton was involved in a lot of campaigning for fellow Democrats, who mostly lost their Senate and Gubernatorial races.
Joe Biden also was hurt, simply by association with President Obama, as the loss of the Senate was a blow to the administration and the Vice President.
But other potential Democratic nominees also suffered from the midterm elections.
Virginia Senator Mark Warner, considered a moderate alternative to most other potential Democratic candidates, struggled to win a close victory over Ed Gillespie, when polls indicated he would have an easy ride to reelection, so this might have affected any plans he had to run for President.
Maryland Governor Martin O’Malley, also considering a Presidential bid, was hurt by the surprise defeat of his Lieutenant Governor, Anthony Brown for the Governorship. losing to Larry Hogan, the Republican nominee in a very “blue” state. Maryland has had only two previous GOP Governors in the past 50 years, Spiro Agnew and Bob Ehrlich.
Massachusetts Senator Elizabeth Warren, also flirting with running for President, was not helped by a surprising Republican victory in the Gubernatorial race, with Charlie Baker defeating State Attorney General Martha Coakley, who also lost the 2010 Senate race to Scott Brown, who succeeded Ted Kennedy. Massachusetts has been strange in the reality that it has elected a number of Republican Governors, while the Democrats dominate the state legislature, and House and Senate races, with the brief exception of Scott Brown for three years.
It is likely that these temporary blows, to five leading potential nominees on the Democratic side, will have no long lasting effect, with the Democrats still having an overwhelming edge in the Electoral College for the 2016 Presidential election.
Republicans are trying everything they can to cheat: http://www.cnn.com/2014/11/17/politics/twitter-republicans-outside-groups/index.html?hpt=hp_t1