The veteran politician fires the starting gun on what looks to be a limited race for the Democratic nomination. Clinton starts the race with a vast amount of money and unrivalled ground operation.
Few Democrats are likely to throw their hat in the ring to challenge the former secretary of state who commands a wide base of support in the party. Senator Elizabeth Warren, who has become something of an icon on the American left, has ruled out running for the Presidency in 2016.
However, that hasn't stopped many who regard Clinton as too moderate urging the Senator to run on a populist left-wing platform. When asked whether she would endorse Clinton for the nomination, Warren replied:
Well, I think we have to see what she says she wants to run on.
Many are unhappy with Clinton's more hawkish nature of foreign policy and worry the Clinton brand doesn't carry the same weight it once did. Clinton controversially backed George W. Bush over the Iraq war that was wildly unpopular among the Democratic base.
The Clinton operation starts with huge advantages, but an outsider could make still successful play for the nomination. It happened before in 2008 when many pundits as well as the thought it was a near certain Clinton woul win the nomination.
But a charismatic Senator called Barack Obama captured the party's imagination and surged to victory in a bitterly fought contest. Obama went on to win two Presidential elections by comfortable margins. The bruising contest is believed to have left a significant amount of bad blood between the Obama and Clinton camps.
Clinton's campaign is gearing up to focus on economic opportunity for the middle classes and the wealth gap between rich and poor. While the Democratic field may be unusually narrow, the Republican nomination is likely to be an intensely fought contest with wide field.
Two Senators have already declared their intention to run for the GOP nomination - Ted Cruz of Texas and Rand Paul of Kentucky. Paul has long taken aim Hillary Clinton targeting her foreign policy views and record as secretary of state.
Although Clinton is favorite to win in 2016, the polls suggest she might not have as an easy ride against her GOP opponent as some may have thought. A survey from Quinnipac University found that Paul led Clinton in two battleground states - Iowa and Colorado. However, Paul trails many of rivals for the Republican nomination.