At this time, in February 2013, it seems very likely that Texas and Florida, the second and fourth largest states in population and electoral votes, will decide which party will win the White House in 2016.
The Democrats have a good chance to win Texas, as it is starting to turn “Blue”, with the growing Hispanic and Latino vote in that state with 38 electoral votes. Hillary Clinton, in particular, would have an excellent chance to win the Lone Star State if she ends up as the Democratic Presidential nominee, but even other Democrats would have a chance to win .
At the same time, with Florida (29 electoral votes) having gone to Barack Obama twice, the Democrats would have a good opportunity to win it next time as well, particularly with Hillary Clinton or Joe Biden as their nominee.
With the other large populated states in the hands of the Democrats for sure (California, New York, Illinois, Pennsylvania, Ohio, Michigan), it is these two states that will decide the election, although if the Democrats can win everything they won under Obama, they do not need Texas. But if they also win Texas, then they would have a literal landslide in the Electoral College, with 370 electoral votes!
So that is why Marco Rubio or Jeb Bush are the best nominees the GOP can run, with a good shot at winning the Sunshine State, and keeping control of Texas, with its Hispanic-Latino vote and the Bush family connection with the Lone Star State.
But again, IF the Democrats just win all the 26 states they won in 2012, or even if they lose some, they will still win the White House. But these two large states are where much of the action will likely be in 2016!