Of the hundreds of handmade signs I saw at the Philadelphia Women's March on Saturday, the one that has stayed with me the most was from an older woman named Eleanor, who hails from Bucks County.

Her poster read, "I cannot believe I still have to protest this s-."

I totally got her frustration. But her sign suggested that the job of ensuring a woman's most basic rights - to make her own reproductive choices, to equal pay, to a leveled field of employment opportunities - is something that can actually be fully accomplished.

Frankly, I don't think those rights will ever be a done deal. Every time women make progress toward walking shoulder-to-shoulder with men, a backlash follows. And we learn anew that opponents to progress have just been hiding in plain sight, waiting for a new opportunity to pounce.

A lot of women thought that electing the country's first female president would equal a giant leap forward for the cause of women's equality. The championing of human rights - from gay marriage, to national health care, to the Lilly Ledbetter Fair Pay Act - had been such a hallmark of the Obama years, it seemed that the election of Hillary Clinton was the next logical step to closing the equity gap.

Instead, Clinton became a victim, emails notwithstanding, of the backlash we should've seen coming, given our history.

Women's marches in Philly and Washington: Our live blog replay.

But you know what? After Saturday's extraordinary march in Washington - and in nearly 700 sister locales in the United States and around the world - I'm thinking that Donald Trump might actually be the best thing that ever happened to the feminist movement.

Clinton's defeat showed a lot of women just how complacent they'd gotten. What else but complacency lets a majority of American women elect a man poised to nominate only Supreme Court justices who'd abolish Roe v. Wade? Who has nominated as Health and Human Services secretary a man hell-bent on defunding Planned Parenthood? Whose new vice president believes women should be permitted to abort only if their pregnancy has resulted from a "forcible" rape?

Complacency allowed a small enough number of women - about 100,000, sprinkled over a handful of states - to bump Trump into office by voting for him or for an unwinnable third-party candidate or by just sitting out the election.

"It's my vote," an acquaintance told me on Nov. 8, saying her conscience wouldn't allow her to cast a ballot for old crooked Hillary, whom she presumed would win anyway. Now, she's horrified by what Trump's presidency might mean for the young daughters she's raising.

We can hardly look each other in the eye right now.

What she forgot - if she ever knew it - is that principles without influence (as a young friend once described it) are of no value in politics. As a result, we have a president who has influence without principles.

On Saturday, that reality was terrifying enough to bring newly awakened women stampeding to our public squares to protect rights they once thought were theirs for keeps.

If Hillary Clinton had won the White House, who knows how the complacency might have worsened, becoming too slack and tepid to handle the next assault on our rights?

Hundreds of thousands of American women - and millions more worldwide - may never have realized that their rights are always at risk if not for a new president who woke them from a cozy fantasy that told them otherwise.

One protester really seemed to get it. As her big, colorful sign proclaimed, "I'm in this for the long haul."