Opposition continues to build against a bill requiring doctors to perform an ultrasound before performing an abortion and women’s rights groups are optimistic it’s enough to force a significant overhaul of legislation before it's sent to Gov. Bob McDonnell.

For a second consecutive day, Republicans in the House of Delegates skipped voting on the bill for at least another 24 hours. While they fended off an effort by Democratic leadership to shelve the bill entirely, pressure against the measure is mounting.

Hundreds of protestors marched around the Richmond Capitol Monday in opposition to the bill and a coalition of abortion-rights groups will present to McDonnell Wednesday 30,000 signatures objecting to the surge in anti-abortion legislation this session, NARAL Pro-Choice Virginia Executive Director Tarina Keene told The Washington Examiner.

If the bill passes, many women would have to undergo a transvaginal ultrasound before an abortion because it’s often the only way doctors can see the fetus in the early stages of a pregnancy. Abortion-rights groups have rallied opposition to the measure around that point, insisting it forces women to undergo an invasive procedure against their will.

A recent Christopher Newport University/Richmond Times-Dispatch poll found 58 percent of Virginians oppose the ultrasound bill, with just 31 percent supporting it.

Del. Charniele Herring, D-Alexandria, is expected to present an amendment authored by NARAL that would instead make the ultrasound procedure an option doctors must offer women, Keene said. That would have been shot down earlier, when Republicans were killing numerous Democratic amendments aimed at softening the bill, but it might be seen more favorably as national media and late-night comedians weigh in on Virginia’s conservative social agenda under GOP stewardship.

“I think both sides are feeling some pressure to make this either go away or at least to reduce it’s power,” Keene said.

The Senate and House both passed identical versions of the bill and McDonnell indicated he would sign it. But the House bill is still in a Senate committee and the Senate version awaits a vote from the full House, where Republicans hold a 2-to-1 majority and should have been able to pass it easily after having approved it once already.

The bill also requires doctors to offer women a copy of the ultrasound and audio of the fetus' heartbeat before conducting an abortion. It requires a 24-hour waiting period between the ultrasound and the abortion.

Even the pro-life Rutherford Institute, the architects of the equally controversial "personhood" bill in Virginia, came out against the ultrasound bill, citing constitutional concerns.

"It is completely inappropriate for the state to require that doctors carry out such invasive procedures on a woman,” said John Whitehead, the organization’s president, in a letter to McDonnell. “If the Fourth Amendment to our Constitution stands for one thing, it is the privacy and bodily integrity.”