Paul Ryan is known around Washington as a budget wonk, the Republican legislator with big economic ideas. Antiabortion groups see something else in Romney's vice presidential pick: a stalwart opponent of abortion rights.

Ryan is hardly the face of the antiabortion movement. He has not introduced a single abortion-related bill during his 12-year tenure in Congress. "You don't expect him to always be your point person on a particular piece of legislation," says Americans for Life Action President Charmaine Yoest.

Yoest expects something different from Ryan: a quiet but unwavering antiabortion stance from one of the top House Republicans. Ryan does not necessarily have to wade into abortion issues, which fall squarely outside his purview as chairman of the House Budget Committee.  But he does, repeatedly: Yoest points out that Ryan has co-sponsored every piece of legislation her group has endorsed.

He has 100 percent "pro-life" rankings from AUL and the National Right to Life Committee. His NARAL Pro-Choice America ranking, meanwhile, is zero.

"It speaks to his integrity," Yoest says. "We know our issue might not be the first thing in line. But when it comes up, we know he'll defend it capably without trying to change his views."

Ryan has proved a reliable vote for abortion restrictions, supporting laws that banned a late-term abortion technique (commonly referred to as "partial birth abortion") and barred the transportation of minors across state lines to terminate a pregnancy. In 2011, he pushed back vociferously against Mitch Daniels's call for a truce on social issues, arguing to the Weekly Standard that he would "never not vote pro-life."

Most recently, Ryan has gained attention for supporting the Sanctity of Life Act, a bill that would declare that "human life shall be deemed to begin with fertilization." The legislation would effectively overturn Roe v. Wade and reflects a growing pro-life push, largely led by state-level advocates, to take more aggressive action to outlaw abortion rather than pursue more piecemeal restrictions on access.

Personhood is a controversial issue, even among pro-life legislators.The Sanctity of Life Act hasn't gained widespread support in the House. It has 62 co-sponsors, meaning about a quarter of House Republicans have signed on. Mitt Romney has declined to sign on to a pledge promising to " work to advance state and federal laws and amendments that recognize the unalienable right to life of all human beings as persons at every stage of development."

Ryan, meanwhile, is sponsoring the Sanctity of Life Act — for a second time. He also supported it in 2009, when it was introduced by Rep. Phil Broun (R-Ga.).

"I cannot believe any official or citizen can still defend the notion that an unborn human being has no rights that an older person is bound to respect," Ryan wrote in a piece on personhood for the Heritage Foundation in 2010. "How long can we sustain our commitment to freedom if we continue to deny the very foundation of freedom — life — for the most vulnerable human beings?"

Ryan also used that piece to explore the connections between economic and social policy, tying his support for free markets and capitalism to his pro-life views. "As a champion of capitalism, I strongly support every person’s right to make these economic choices and to fight against government efforts to limit them," he wrote.

That's what Yoest likes the most when she looks at Ryan as an antiabortion candidate: He doesn't need to make space for such issues in his economic platform. But he has before, and she hopes he'll continue to do so.

"He's not a duck and run person," Yoest said. "People have different roles in the movement. This is a guy who is chairman of the budget committee, who has places to go and people to impress, and he writes this major piece on this. That's really important to us."