Abortion and birth control are back in the news — the latest reminder that hot button social issues will continue to be part of the presidential race. The House is taking up a bill that prohibits abortions driven by gender concerns, with a vote scheduled for today. Meanwhile, Planned Parenthood is unleashing ads targeting Mitt Romney on his acquiescence to House plans to cut off funding to that organization.

This is a bit of a surprise. Why? Usually in political messaging, a lot of the battle isn’t over what to think — it’s what to think about. Barack Obama would love voters to think about Mitt Romney’s record in Massachusetts and flip-flops…really, the Obama campaign just wants people to think about Romney, and not just about Obama. Republicans want people to think about unemployment. Generally, you can tell from what the campaigns talk about exactly what topics they want to campaign on, and most of the time the two sides differ on this dramatically.

That’s why it’s always fascinating when both sides want people to focus on the same thing. We’ve seen this with the House Republican budget, which Paul Ryan insisted on bringing to the floor despite the obvious fact that it was going nowhere — and which Democrats were also eager to talk about. Now, we have both sides wanting voters to focus on abortion and birth control.

The House vote targets what Republicans clearly see as a winning wrinkle in the abortion wars: abortion for the purpose of sex selection. While for Planned Parenthood, the issue in their ads isn’t stated as abortion at all; in their words, it’s about “birth control and cancer screenings.” It’s also worth noting that in neither case is this actually the Romney or Obama campaigns acting, and it’s unclear whether they would approve of the focus adopted by their allies.

Still, it’s striking that both sides seem to be inviting voters to focus on this area. More than anything, it’s a good reminder that we’re in an era of partisan campaigns that go beyond what just presidential candidates might want to run on. We’re not just electing a person, but more than anything we’re electing a party, which means among other things a set of interest groups. That means that the candidates can’t always control what issues they want to talk about. And so issues such as abortion, birth control, and gay marriage will continue to pop up — with unpredictable consequences for the presidential race.

This also means that whoever takes office in January will be constrained into carrying out his party’s agenda on everything — social issues included. Which in turn means that anyone who thinks a President Romney would have the leeway to govern as a moderate is kidding himself.