The anxious-looking women talk directly to the camera, warning that the Colorado Republican running for the US Senate opposes the state's reproductive rights law and supports the conservative Supreme Court justices who revoked the constitutional right to abortion this summer.

“It's not even close,” one says as the ad for the incumbent Democratic senator wraps up. “We need Michael Bennet fighting for us.”

The spot is significant because the man it slams on abortion, businessman Joe O'Dea, is a rare Republican supporter of at least some abortion rights.

O'Dea said he would back a law to codify the protections of Roe v Wade, though he opposes abortions after 20 weeks except in cases of rape, incest or to protect the life of the mother.

Analysts say similar nuanced positions were once considered the political sweet spot in the complex world of abortion politics, coming closest to representing the views of the typical, conflicted voter.

But that may be changing as abortion restrictions kick in following the fall of Roe with the high court's ruling in June.

“We are here in this country, right now, with patients travelling thousands of miles for care because politicians have been given the room for the least little bit of nuance,” said Adrienne Mansanares of Planned Parenthood Action Colorado during a recent news conference to back Bennet.

The message from Democrats: Republicans can't be trusted on the issue — regardless of their personal beliefs.

Abortion has become an increasingly partisan issue over recent decades, but public views have always been more shades of gray than black and white.

Typically, support for abortion rights is highest for women in the earliest stages of pregnancy and tapers off as the pregnancy advances, until it is lowest for abortions very close to delivery, said Jocelyn Kiley of the Pew Research Centre.