The Clinton campaign went into overdrive this week to shore up support among voters most assumed would have been locked in as Clinton backers from the start—Democratic women.

From last Saturday’s kickoff of “New Hampshire Women for Hillary,” to Clinton’s appearance on The Ellen DeGeneres Show last Thursday where she pitched, “If you vote for somebody on the merits, one of my merits is that I’m a woman,” to an online campaign store newly stocked with lady-friendly merch (official “Women’s Rights are Human Rights” tote, anyone?) the not-at-all subtle message is this: Hey ladies, vote for Hillary!

The female hard sell is coming as a series of local and national polls show that Clinton’s strength among Democratic women voters has continued to steadily, and in some cases, precipitously erode as her campaign has become bogged down in questions over use of a private email server and Sen. Bernie Sanders has risen on a wave of populist support that the Clinton camp had mostly dismissed or ignored.

The latest bad news for Clinton came last week from the NBC News/Marist poll Sanders Leads Clinton by 9 in N.H., Gains in Iowa: Poll, which showed Clinton losing to Sanders by nine percentage points in New Hampshire, thanks mostly a huge drop in Clinton’s female support. Although Clinton still held onto women by seven points, her lead among women there is down 16 points since July. The same holds true in Iowa, where Clinton’s lead among Democratic women shrank 24 points between July and September. A previous PPP poll showed Clinton losing New Hampshire women to Sanders by three points.

“I think there is concern on her campaign about the gender gap, which has gotten significantly narrower since our poll in July,” said Lee Mirengoff, the director of the Marist poll. “The campaign seems to understand that although they have a firewall they are trying to build in the South, women are really what this campaign’s strongest base is and they don’t want any slippage there.”

The slide among Democratic women in New Hampshire and Iowa mirrors a series of national polls that show Clinton’s performance among women on a steady downward trend. A CNN/ORC poll conducted in December 2014 (PDF) showed that Clinton entered the Democratic primary contest with an enormous advantage among women over any opponent, with 75 percent saying they’d vote for Clinton and just 2 percent for Sanders.

As Sanders’s crowds at campaign rallies grew into the thousands and Clinton was dogged by media questions about her email server over the summer, Clinton’s support among Democratic women nationally dropped to 51 percent by the end of August, with Sanders’s up to 27 percent.

Perhaps more worrisome, women don’t seem to think she’s telling the truth about her server. Among all female voters, 51 percent in a Fox News poll said Clinton “knowingly lied” about her private server, while 51 percent of women in CNN’s August survey said Clinton did something wrong when she decided to control her email through her own server.

Clinton’s slide among her core constituency hasn’t gone unnoticed by her Republican rivals. “It appears that Democratic women are starting to trend the way of the larger electorate,” said Kellyanne Conway, a longtime Republican pollster who is working for the Ted Cruz campaign this cycle. “They don’t trust her, and they don’t see her projecting confidence in herself, in them, or in the future of the country.”

Conway said that from Republicans’ perspective, Clinton would need to outperform Barack Obama’s 56 percent showing among women voters in 2008 in order to win a general election contest in 2016. "Knowing that women will comprise a majority of the electorate and knowing that she will under-perform among men compared to President Obama and President Clinton, she needs to get closer to 58 percent to 60 percent among women and right now she is nowhere near that.”

Clinton’s campaign counters that her relative strength in general election polls is what really matters and it’s true that Clinton quickly consolidates Democratic women’s support in hypothetical head-to-head match-ups against Donald Trump (PDF).

But even that support appears to be slipping.

In the latest CNN/ORC poll, Clinton’s lead with women has vanished (PDF) when she is matched up with neurosurgeon Ben Carson and Jeb Bush.

But the real danger for Clinton in a general election isn’t that Democratic women will vote for the Republican. The danger is that some of those women will not vote at all.

“The likelihood is the Democrats will carry the women’s vote, but the question is the magnitude of that and the turnout,” Marist’s Lee Mirengoff said. “But first things first. There are a dozen make-or-break days between now and the end of September.”

Which days will be make or break for Clinton? “Every day,” Mirengoff said.