Scott Walker is expected later this week to sign a ban on abortions midway through pregnancy, making him the third GOP presidential candidate to approve such a measure.

It's not surprising the Wisconsin governor, who officially jumped into the Republican contest on Monday, would support the bill, which bans abortions past 20 weeks of fertilization unless the mother's life is at stake.

But Walker's move adds another Republican to a growing list of presidential candidates who have helped build momentum behind 20-week bans, which have been passed by more than a dozen states in recent years. And it adds fuel to the 2016 political fire around the issue of abortion, which continues to hotly divide the country.

"This common-sense, compassionate stand is not only morally just, it is smart politics," Marilyn Musgrave, vice president of the Susan B. Anthony List, a lead group promoting 20-week bans.

Walker had already endorsed a federal version of the legislation sponsored by Sen. Lindsey Graham, which the Senate is expected to vote on sometime this year. And he's got a long history of backing anti-abortion causes, including signing a 2013 law requiring women seeking an abortion to view an ultrasound first.

"Walker is callously trying to trade women's health for the support of a few special interest groups — but we know these are losing issues for the American people," said Planned Parenthood President Cecile Richards. "Unfortunately, in Walker's transparent appeal to the far right of the Republican Party, it's the women of Wisconsin who pay the price."

Two of Walker's Republican opponents have approved similar laws in their own states. Louisiana Gov. Bobby Jindal signed a 20-week ban in 2012, and former Texas Gov. Rick Perry followed suit a year later.

Graham, who also is seeking the GOP nomination, has been championing a 20-week ban in Congress over the last year and a half. Walker, Jindal, Perry and the rest of the leading Republican candidates have all endorsed Graham's measure, according to a count kept by SBA List.

The Wisconsin Assembly easily passed the measure last week, which already had been approved by the Senate, sending it to Walker's desk.

"Thanks to the members of the Assembly for voting to protect an unborn child when he or she can feel pain, at five months," Walker tweeted last week.

Known as "fetal pain" laws, the measures are based on the idea that a fetus can feel pain midway through a pregnancy, which the American Congress of Obstetricians and Gynecologists contests.