Suddenly, more Americans are pro-life than are pro-choice.

Look at the flip from '08 to '09. The shift took place within the GOP, it's important to see. Democrats did not change. But why did the change take place? The big difference between '08 and '09 is that Obama took over the presidency:

With the first pro-choice president in eight years already making changes to the nation's policies on funding abortion overseas, expressing his support for the Freedom of Choice Act, and moving toward rescinding federal job protections for medical workers who refuse to participate in abortion procedures, Americans -- and, in particular, Republicans -- seem to be taking a step back from the pro-choice position. However, the retreat is evident among political moderates as well as conservatives.

It is possible that, through his abortion policies, Obama has pushed the public's understanding of what it means to be "pro-choice" slightly to the left, politically. While Democrats may support that, as they generally support everything Obama is doing as president, it may be driving others in the opposite direction.