This is hardly the first time it has looked as if Hillary Rodham Clinton’s presidential ambitions were on the ropes, and each time she has found a way to bounce back. But as she heads into critical Democratic primary contests in Nevada and South Carolina, the former Secretary of State’s campaign seems to be reeling.

After the 22-point shellacking administered by Vermont Sen. Bernie Sanders in New Hampshire last week and her squeaker of a win in the Iowa Democratic caucuses the week before, Clinton has been counting on a couple of solid performances in the Nevada caucuses on Saturday and the South Carolina primary a week later to demonstrate her appeal in more racially and ethnically diverse terrain.

Related: Clinton’s Lead in Nevada Evaporates as Sanders Continues to Surge

But as hard as she tries to portray Sanders as a Johnny One Note on income inequality and the evils of Wall Street, with little appeal beyond college campuses and progressive strongholds, he continues to confound her with shrewd tactics, mass rallies, aggressive and well-staffed ground operations and a gold-plated media campaign — all thanks to unprecedented grassroots fundraising.

Clinton’s one-time air of invincibility has given way to pangs of desperation and lowered expectations of how well she will do in Nevada and South Carolina. Jon Ralston, a veteran political reporter in Nevada, wrote on Tuesday that “the Clinton panic is palpable” and that “no one on either side has asserted the race is not in reach for Sanders.”

Saturday’s Nevada Democratic caucuses were once touted as a field day for the former First Lady and New York Senator because of her close ties to Hispanic voters and powerful labor union leaders. Yet Sanders has made inroads with the young, working-class Latinos and rank-and-file union members.

Similarly, Clinton was thought to hold a huge edge over Sanders in South Carolina because of its large African-American population, but that was before Sanders showered voters with promises of free college tuition and health care and spoke out angrily about police violence against young blacks and the inequities of the criminal justice system.

Related: Clinton Scrambles as Sanders Puts the Black Vote in Play

“Clinton has every advantage and should win handily in South Carolina,” University of Virginia political scientist Larry J. Sabato said on Tuesday in an email. “If she loses or it is close, the calls to [Vice President] Joe Biden will start.”

“If Clinton does well [on Super Tuesday] on March 1, she’ll regain her traction,” he added. “If not, Biden will have to install more lines.”

Any thought that Biden might ride to the rescue of the Democratic Party after taking himself out of the race late last year is remote at best. But it helps to underscore that Clinton’s problems are legion and may in the end be too great to surmount against the surging Sanders.

She suffered incalculable damage from Republican attacks against her for her ill-advised use of personal email for top-secret government business during four years at the State Department and her role in the lead up to the terrorist attacks against a U.S. diplomatic compound in Benghazi, Libya.

Clinton and her husband, former President Bill Clinton, turned off many voters by cashing in after their government service by accepting hundreds of millions of dollars in speaking fees and honoraria from special interest groups and universities. Dozens of polls in recent months confirm that while Democratic voters view her as more experienced and better prepared than most to lead the country, shockingly high majorities say that they question her honesty and integrity and don’t believe she has their best interest in mind.

Related: How Bernie Sanders Just Shook Up the Democratic Primary. Again

In a new era of politics in which voters fawn over anti-establishment candidates like Donald Trump and Sanders as they shatter political traditions, Clinton finds herself at a huge disadvantage. She is offering herself as a “pragmatic progressive” who would take a commonsense approach to winning support in Congress for a realistic agenda — hardly an exciting selling point to many young voters.

During a nationally televised Democratic debate last weekend, Clinton said that if Sanders’ agenda of national health care for all, free college tuition, and other expanded social programs were enacted, it would increase the federal government by 40 percent and drive the deficit into the outer-stratosphere. While Sanders and his campaign advisers argue that his proposals would all be offset by higher taxes – mostly on the rich and Wall Street traders – Clinton and some independent analysts insist that the Vermont senator’s numbers “don’t add up.”

According to The New York Times, some left-of-center economists have concluded that Sanders’ proposals would add $2 trillion to $3 trillion a year on average to federal spending. President Obama’s fiscal 2017 budget calls for total government spending of a little more than $4 trillion. While Clinton and other critics may dismiss Sanders’ proposals as budget fantasy and wishful thinking, many of the Democrats rallying to his side view those plans as exciting and inspiring.

Clinton could still win in both states – especially if her voter turnout operations prove to be far better than they were during the first two contests. But in both cases, Sanders will demonstrate that he commands support from a much wider slice of the electorate than Clinton’s camp has been willing to acknowledge.

And even if Clinton ultimately prevails — with the help of “super delegates” and more conservative voters throughout the South, Midwest and West — the Democratic campaign will likely prove to be a tough slog all the way to the Democratic National Convention this summer. In 2008, Clinton fought another long, hard primary battle against Barack Obama, only to lose.

Related: Sanders' Landslide Win in New Hampshire Puts Huge Pressure on Clinton

One saving grace for Clinton is that she has held substantial, double-digit leads over Sanders in national polling, suggesting that there is still a large reservoir of support for her once the campaign moves into high gear. However, a NBC News/Survey Monkey Tracking Poll released today shows Clinton leading Sanders by just 10 percentage points — 50 percent to 40 percent, her smallest margin in seven weeks.

What’s more, a third of Democratic or Democratic-leaning voters say they now believe Sanders will be the eventual nominee. That’s more than before, but it still leaves two thirds of Democrats convinced that somehow Clinton will prevail in the end.

A Washington Post report out of Nevada nicely encapsulates Clinton’s problems in repelling a tough challenge from Sanders. A multi-ethnic coalition of Sanders supporters, energized by his promises of big social spending programs, immigration reform and social justice, are eager to dump the presumed Democratic frontrunner in favor of the self-styled democratic socialist.

A dozen Sanders campaign offices have sprung up across the state, from Las Vegas to Reno, with more than 100 paid staffers. And Sanders — who raised over $6 million following his big victory in New Hampshire — is outspending Clinton on TV ads by roughly 2 to 1, according to the Las Vegas Review-Journal. Many of the ads target Spanish-speaking voters.

Jeff Weaver, Sanders’ campaign manager, told The Washington Post that a victory in Nevada is a chance to disprove “this firewall fantasy that the Clinton campaign has put out there.”

“If we do well, it destroys that myth,” he said.