One caveat: "You have to be okay with being led by women," she said.

"A lot of men are quiet supporters of women," said Jackson Katz, author of "Man Enough? Donald Trump, Hillary Clinton, and the Politics of Presidential Masculinity." Millions of men voted for Clinton and support women's rights both politically and personally, he said, but they don't have a powerful voice.

Katz attributes the more muffled support among men in part to efforts that Trump and other Republicans have made to challenge the masculinity of men who support liberal causes or women in leadership. Trump has repeatedly cast himself as the strong man.

Alex Mohajer, co-founder of Bros 4 Hillary, an advocacy group, said it this way: "There is a sense [that] if you outwardly support a woman you are less deserving of your man stripes."

Katz said these men will need to speak out if they don't want to see abortion outlawed, given Trump's pledge to appoint antiabortion judges to federal courts.

"That means taking some risks in challenging other men, and literally standing up to the bullying that comes from the right about masculinity," Katz said.

Women are leading the charge for the march, heading up logistics and legal work, while male volunteers are playing mostly supporting roles.

Tim Riddick, a 36-year-old photographer from Woodbridge, said he plans to join the march because he wants to set an example for his three young sons.

Riddick calls himself a "purple elephant," a rare liberal who is also an observant Christian. He believes... blending the line on what is considered a "women's issue" to start with, including access to abortion and birth control.