well we have a government that tries to represent the will of the people. If most Americans really wanted abortion to be legal, they would do anything to prevent a pro-life president from winning.
Pro-life candidates lost in '76, '92 and '96 and in 2000 the pro-life candidate won despite receiving less votes than the pro-choice candidate. The reality of the situation is that voters a.) no longer really care that much about abortion and b.) realize that a pro-life president probably isn't going to do much to change the status quo.
Do the math. It is fair to say by looking at the last two elections that about 1/2 the voters support the pro-choice democrat and the other 1/2 the voters support the republican candidate. Currently, the republican frontrunner is himself, pro-choice.
Kinda starting to look like a consensus, doesn't it?