Hillary Clinton is seen aboard the campaign bus in Cleveland on the third day of a bus tour through Pennsylvania and Ohio.

July 31, 2016 Hillary Clinton is seen aboard the campaign bus in Cleveland on the third day of a bus tour through Pennsylvania and Ohio. Melina Mara/The Washington Post

The former secretary of state, senator and first lady is the Democratic nominee for president.

Former secretary of state Hillary Clinton campaigns in key states in her quest to become the Democratic nominee for president.

Former secretary of state Hillary Clinton campaigns in key states in her quest to become the Democratic nominee for president.

With another Iowa presidential contest at risk of slipping out of Hillary Clinton’s reach, the Democratic Party is launching a massive effort this weekend to boost her candidacy.

A crowd of well-known entertainment and political figures, including Sen. Timothy M. Kaine (Va.), a former party chairman, and Tony Goldwyn, star of the hit series “Scandal,” is jetting to all corners of this state to help Clinton erase her enthusiasm deficit to Sen. Bernie Sanders (Vt.).

And major progressive groups such as the Planned Parenthood Action Fund and the National Education Association are firing up their political operations, including door-knocking teams and phone banks, to give her an outside push.

The campaign and its allies had planned all along to escalate their efforts at this point, as the caucuses near. However, Democratic governors, senators and other party leaders said they are increasingly alarmed at the prospect of Sanders, a self-described democratic socialist, surfing a wave of populist frustration to the nomination. And they were quick in interviews this week to dispense advice to Clinton.

Get feisty and real, they said. Open your heart. Find visceral ways to show people how you would fix their problems. Most of all, throw that Clintonian caution to the wind and sharpen your attacks on the senator from Vermont: Challenge his knowledge of foreign affairs, his single-payer health-care plan, his temperament and his ability to forge consensus in Washington.

Democratic presidential candidate Hillary Clinton, right, hugs pop singer Demi Lovato at a rally on the campus of University of Iowa on Thursday. (Jae C. Hong/AP)

These Democrats said Clinton should call for more debates so she can prosecute the case against Sanders. They said it is imperative for her husband, former president Bill Clinton, to assume an even greater role in crystallizing the choice for Democrats.

“It’s important that she draw more contrasts with Sanders without ticking off his supporters,” said former New Mexico governor Bill Richardson, a Clinton endorser. “Do it carefully, do it succinctly, but you have to do it because this is when voters are picking candidates. You can’t run a statesman-like campaign now.”

[Sanders camp calls Clinton ally David Brock a ‘mudslinger’]

In the 2008 campaign, Clinton was at her best when she was losing to Barack Obama. As she is under siege anew this year, her allies said they hope to see her return to that performance level.

“She’s no stranger to this,” said Kaine, a top Obama backer eight years ago who now supports Clinton. “In ’08, she was always stronger when pressed — after Iowa, then in New Hampshire; after Super Tuesday, then in states like Ohio and Pennsylvania. She was always, always better when the going got tough.”

Sen. Claire McCaskill (Mo.), another Clinton convert from the Obama team, said: “She does her best work as an underdog. She’s got amazing determination and grit.”

In the final week before the caucuses, Clinton is relying heavily on the formidable ground organization her campaign began building last spring. She has invested heavily in Iowa, viewing the caucuses, where she finished a devastating third in 2008, as the top priority this time around. Her campaign long ago recruited volunteers in all of the state’s 1,680 precincts and for months has been surgically targeting likely caucus-goers.

A volunteer at Democratic presidential candidate Bernie Sanders' Jan. 19 event in Fort Dodge, Iowa, wears a shirt decorated with Sanders' image. (Jim Young/Reuters)

Long considered Clinton’s to lose, the Iowa race is now a dead heat, with some recent public polls showing Sanders inching ahead. Sanders has scaled up his ground organization and is spending heavily on television advertising.

This week, he boarded a hulking new bus and barnstormed the state, staging the large rallies that have become his signature as well as more intimate events in rural areas.

“You tell me: Which campaign, objectively speaking, is creating the energy and the enthusiasm for a large voter turnout?” Sanders asked reporters Tuesday. “Everybody knows that it is our campaign.”

From Day One, the mantra from Clinton’s New York headquarters has been to prepare for a competitive primary, starting in Iowa.

As Delaware Gov. Jack Markell said, “I don’t really remember a Democratic primary that was not competitive.”

Publicly at least, Clinton’s senior advisers project calm and composure. In the tightening polls, they see a silver lining: Her supporters have been shaken awake, erasing fears of complacency.

On the ground here, there has been a noticeable difference between Clinton’s events and Sanders’s, where a seemingly more organic enthusiasm is on display. To close that gap, Clinton is deploying star power.

Thursday night, she rallied with pop singer Demi Lovato at the University of Iowa’s student union, a hive of Sanders fans.

This weekend, actors Goldwyn and Jamie Lee Curtis; Sens. Kaine, Cory Booker (N.J.) and Kirsten Gillibrand (N.Y.); and Housing and Urban Development Secretary Julián Castro are fanning out across Iowa for their own organizing events.

Clinton campaign manager Robby Mook said he regrets that there are not more days on the calendar for the Clintons to campaign in Iowa. “Honestly, I just wish we had more time to get her and President Clinton out to talk to people,” he said, noting that about half the attendees at these events sign “commit to caucus” cards pledging their support.

Outside groups backing Clinton are helping with phone banks and social-media outreach, and by showing up at her events.

At a rally in Vinton, members of the NEA, the nation’s largest teachers union, came out in force wearing T-shirts, pins and stickers, and waving signs. The union’s state chapter, the Iowa State Education Association, which has 35,000 members, also worked with the campaign to identify some precinct captains.

“We want to win,” chapter President Tammy Wawro said. “This is the bottom line, and we need to come out of the gate with a candidate that can win.”

After the Human Rights Campaign endorsed Clinton this week, the gay rights group’s staffers in Iowa have been urging members to caucus for her. President Chad Griffin will officially endorse Clinton on Sunday in Des Moines.

Also providing a lift is Emily’s List, which recruits and supports female candidates and was an early Clinton ally. President Stephanie Schriock spent Thursday and Friday rallying Clinton volunteers and organizers at eight stops in Iowa.

“This is actually what we do as progressives,” Schriock said.

After giving Clinton its first-ever primary endorsement, Planned Parenthood adopted a “whatever it takes” strategy to support her in Iowa. The group sent mailers, organized phone banks and plans to soon release digital ads on Clinton’s behalf. President Cecile Richards is holding her own events here Saturday and Sunday.

Another abortion rights group, NARAL-Pro Choice America, has invested in the range of six figures in an effort to boost Clinton in Iowa. With a staff of 10, NARAL is focusing on canvassing in Ames, Des Moines, Cedar Rapids and Iowa City, as well as manning phone banks to reach members in other parts of the state.

Democratic leaders are resigned to the reality that Clinton is in danger of losing both the Feb. 1 Iowa caucuses and, eight days later, the New Hampshire primary, where Sanders has long had a leg up.

“I realize that at this moment in the primary cycle, in both parties, being pragmatic, experienced and visionary isn’t in vogue,” said Vermont Gov. Peter Shumlin, a Clinton supporter.

But eventually, Shumlin said, “voters are going to want to choose someone who is a bright, experienced, capable, pragmatic progressive who has a track record of pulling people together to get really tough things done. That’s Hillary.”

[Sanders camp airs closing campaign ad in Iowa filled with inspired voters ]

Clinton allies find comfort in the calendar. Iowa and New Hampshire are overwhelmingly white states with decidedly liberal Democratic electorates. But next up are contests in Nevada and South Carolina, states that have more diverse and centrist voters, which could play to Clinton’s strengths. Many of the March events are in states across the South and the Midwest, where Clinton is favored.

Within the Democratic elite, where Clinton enjoys near-universal support, the antipathy toward Sanders has grown steadily as he has emerged as a potential Clinton slayer. All week, McCaskill has been loudly predicting an electoral catastrophe if her party nominates Sanders.

“Bernie has labeled himself a socialist — we’re not labeling Bernie as a socialist — and I know what the Republicans will do with that,” McCaskill said Thursday. “They’re going to rip him from limb to limb! . . . I said, ‘They’re going to connect him to communism,’ and [GOP front-runner Donald] Trump did it yesterday.”

Delaware’s Markell, also a Clinton backer, agreed. “If I were a candidate for the Senate or governor or Congress in Ohio or Florida or Missouri or New Hampshire or Pennsylvania, I’d be really, really concerned,” he said.

Clinton’s supporters said she could dispatch Sanders if she adjusted her message. One fix Richardson suggested: “Use Bill Clinton more than they’re doing. He’s an asset. I know there’s all this [Monica] Lewinsky stuff, but people remember the good economy of Clinton.”

Sen. Sherrod Brown (Ohio) said one of Hillary Clinton’s finest moments of late was when she spoke forcefully in last weekend’s debate about the water crisis in Flint, Mich.

“Her rhetoric is not as strong as Bernie’s, but that does not fix these problems,” said Brown, a Clinton supporter. “She can reach people equally by telling their stories and talking about how she’s going to fix them. I’m convinced she can. She’s not doing it as well as we’d like yet, but she will.”

John Wagner in Iowa and Mike DeBonis, Karoun Demirjian, Anne Gearan and Kelsey Snell in Washington contributed to this report.