FiveThirtyEight has devised a pretty brilliant way to illustrate the concept of "paths" to election victory.
So, the idea is that you start from the areas where a candidate is most likely to win (Washington D.C. for Hillary Clinton, Nebraska for Donald Trump.)
That's your foundation. From there, the candidates are trying to reach in to the "center," those toss-up states where the candidates are competing closely.
Now, Colorado is not the most competitive state. FiveThirtyEight gives Clinton 61 percent odds of winning here, while Florida is more like 50-50. But Colorado is the crucial state in this theory.
Basically, FiveThirtyEight favors Clinton to win enough states to win the presidency right now. But they also think that, out of those favorable states, her chances are worst in Colorado. If she wins every single one of those favorable states she wins the election, but Colorado is the weakest link.
Of course, that assumes that nothing surprising happens. If Clinton takes Florida or North Carolina she can lose Colorado. If Trump takes Pennsylvania, he can win without Colorado.
Anyway, I've put a lot of words into explaining something that FiveThirtyEight does beautifully with a chart. Click here and scroll down until you see the weird winding path chart.