But President Barack Obama's re-election team and its allies have also been highlighting the congressman's staunchly anti-abortion stance, hoping to buttress its argument that the Republican ticket is hostile to women's rights.
Ryan has earned a perfect rating from the National Right to Life Committee for his votes during his 14 years in Congress. The National Abortion Rights Action League tallied 59 votes that Ryan took on abortion-related bills. On each measure, he voted against abortion rights.
"I'm as pro-life as a person gets," Ryan told The Weekly Standard, a conservative magazine, in 2010.
Shortly after the formal announcement of Ryan's selection on Aug. 11, Obama's team tweeted that Ryan would ban abortions even in cases of rape and incest and had sponsored a bill that would outlaw some forms of birth control. The Democratic campaign emailed female supporters to stress Ryan's record on women's issues, including his vote against the Lilly Ledbetter Fair Pay Act, the first bill Obama signed when he took office.
When Ryan made his Colorado debut Tuesday, a liberal activist group flew a banner above the high school where he was speaking. The banner read, in part, "Choose me, lose choice." On Friday, the Obama campaign launched a television ad blasting Ryan's abortion record.
Romney's campaign contends that Democrats are trying to confuse voters by attacking Ryan on women's issues. "This is a desperate attempt by President Obama's allies to distract from his failed economic policies, which have been particularly devastating to women," said Brendan Buck, a spokesman for the vice presidential candidate.
In a statement, the Obama campaign said, "American women know they can't trust a Romney/Ryan ticket to stand up for them."
Both campaigns are aggressively targeting suburban women, and the election has already featured an unusual amount of debate over reproductive rights. The entry of Ryan into the race only heightens the polarization over the issue.
"There are lots of things that the pro-abortion community will throw at Paul Ryan because there's lots of ammunition, since he has such a solid pro-life record," said former GOP Rep. Marilyn Musgrave, now vice president for governmental affairs of the anti-abortion Susan B. Anthony List.
In a 2010 essay for a conservative think tank, Ryan compared the U.S. Supreme Court ruling that legalized abortion to the infamous 1857 Dred Scott decision, in which the court ruled that black slaves were not legally people. "After America has won the last century's hard-fought struggles against unequal human rights in the forms of totalitarianism abroad and segregation at home, I cannot believe any official or citizen can still defend the notion that an unborn human being has no rights," Ryan wrote.
When he first won election to Congress in 1998, Ryan vowed to oppose all abortions unless they were needed to save the life of the mother. He voted for a bill requiring that women who receive abortions first undergo an ultrasound, and another barring anyone besides parents from transporting minors across state lines for abortions. He also voted against a measure to allow women in the military to receive abortions in military hospitals.
Ryan was also one of several dozen Republican co-sponsors last year of a bill called the Sanctity of Human Life Act. The measure, which never made it to the House floor, would give a fertilized egg the same legal rights as a person. Abortion rights groups say that would effectively outlaw all abortions, as well as some types of contraception and in-vitro fertilization. Efforts to implement such "personhood" laws at state levels have been rejected even in the most conservative settings.
Mississippi voters rejected a personhood ballot measure in November 2011. In Colorado, a personhood measure is heading to the November ballot even after it was rejected by a 70-30 margin in 2010.
"It's incredibly clear that Paul Ryan is an extreme anti-choice candidate," said Lissy Moskowitz, general counsel for NARAL Pro-Choice America. "He's a leader on this issue."
Romney indicated he backed abortion rights at the start of his Massachusetts governorship before declaring himself "pro-life" in 2005. He has called for ending federal funding of Planned Parenthood and for outlawing all abortions other than in cases of rape, incest or to save the life of the mother - the official stance of the Romney-Ryan campaign.
David O'Steen, executive director of National Right to Life, said Romney's anti-abortion stances in the past two campaigns had reassured many abortion foes, including his group, which endorsed the former Massachusetts governor in April. "But you always looks to see who the vice presidential pick will be and will that be ideologically compatible," O'Steen said. After the Ryan pick, he added, "there's a lot of enthusiasm that I'm hearing from our members and chapters."
Each side in the contentious abortion debate believes the emphasis on the issue will pay political dividends for them, said Elizabeth Shipp, NARAL's political director. While Obama will use the issue to turn out crucial independent voters, Shipp said, Republicans "are going to do everything they can to use this to rally their anti-choice extreme base."
Shipp said she's been stunned by the focus on reproductive issues in this year's campaign, especially compared with 2004 and 2008. In those years, Shipp said, NARAL would send people out with low-key signs to campaign events, where they would have to stand outside, far away from the action.
"Now the president is talking about it. The campaign is talking about it," Shipp said. "When you look at the voting blocks that are going to be there on Nov. 6, I think it's to the advantage of the president to keep these issues front and center."