Colorado Republican Senate candidate Cory Gardner is calling for birth-control pills to be sold without a prescription in a new TV ad, putting campaign cash behind a conservative argument that's been picking up steam in recent months.

In a 30-second ad released Tuesday, Gardner argues for cheaper, over-the-counter access to birth-control pills, an argument he previously made in a June op-ed in the Denver Post.

"I believe the pill ought to be available over the counter, round the clock, without a prescription — cheaper and easier, for you," Gardner says to a group of women in the ad.

Gardner is running a highly competitive race against incumbent Democratic Sen. Mark Udall, but he's not the first one to call for over-the-counter birth control.

In an op-ed in 2012, Louisiana Gov. Bobby Jindal argued that adult women should be allowed to buy birth-control pills without a prescription.

In July, Republican Sens. Mitch McConnell of Kentucky, Kelly Ayotte of New Hampshire and Deb Fischer of Nebraska introduced a bill that called for the Food and Drug Administration to study whether birth control could be made safely available without a prescription.

The push for over-the-counter birth control comes as Republicans look to win over women voters.

Last week, a detailed report put together by two major Republican groups obtained by Politico showed that many women view the party as "intolerant" and "stuck in the past."

In 2013, the American College of Obstetricians and Gynecologists, a leading group of women's physicians, endorsed over-the-counter birth-control pills.