Alarmed by the ascent of Donald Trump, more than 100 celebrities have launched a campaign to defeat the Republican presidential nominee, saying they feel a responsibility to highlight "the real and present threats of his candidacy."

In a letter shared exclusively with Mic, the celebrities — including writer and director Shonda Rhimes, actresses Kerry Washington and Olivia Wilde, actors Mark Ruffalo and Neil Patrick Harris, writer and director Lena Dunham — pledge to "use the power of our voice and the power of our vote to defeat Donald Trump and the hateful ideology he represents."

"When dangerous and divisive leaders have come to power in the past, it has been in part because those of goodwill failed to speak out for themselves or their fellow citizens," the letter states, citing Trump's rhetoric targeting women, Latinos, people with disabilities and others. "Some of us come from the groups Trump has attacked. Some of us don't. But as history has shown, it's often only a matter of time before the 'other' becomes me."

Actress Kerry Washington is among the signatories. Alex Wong/Getty Images

Explaining why she joined the campaign, called United Against Hate and organized by the progressive group MoveOn.org, YouTube celebrity Laci Green told Mic that Trump represented a unique threat to the nation.

"He appeals to darkest tendencies of Americans — and with great charisma," she said. "American progressives must step up right now. Defeating Trump is not a matter of getting the word out that he's basically Voldemort. To defeat Trump, we need to get people, and especially young progressives, to actually vote in spite of frustrations with [presumptive Democratic nominee Hillary] Clinton."

Singer Mary Lambert said she and her fellow entertainers "have the fortuity to influence humanity on a profoundly deep level."

"I personally believe that if I am to promote myself as an entertainer, then I should equally be held responsible for the platform that I have," she said. "There are dire consequences to idly standing by when a hateful bigot like Donald Trump is holding a loaded gun."

Though Trump may welcome the hatred of a group emblematic of the Hollywood elite regularly pilloried by Republicans, he is no stranger to the entertainment world, having served as host of the Celebrity Apprentice and hobnobbed with leading A-listers for decades.

Donald Trump once hobnobbed with top celebrities, but many are now uniting against his candidacy. Brad Barket/Getty Images

Among the signatories is Tony Schwartz, who ghost-wrote Trump's famed book The Art of the Deal and recently told the New Yorker he regretted his work for Trump, saying, "I genuinely believe that if Trump wins and gets the nuclear codes there is an excellent possibility it will lead to the end of civilization."

The campaign's launch comes as polls show Trump benefiting from a national polling bounce following the Republican National Convention. According to the RealClearPolitics polling average, Trump and Clinton are deadlocked at about 44% of the vote — possibly infusing a new sense of urgency into efforts to derail the GOP nominee.

A complete list of the letter's signatories follows:

Mark Ruffalo, actor/director/producer and activist

Shonda Rhimes, writer, director, producer

Ryan Murphy, producer, director

Russell Simmons, entrepreneur and activist

Kerry Washington, actor and activist

Julianne Moore, actor and activist

Shepard Fairey, artist

Adam McKay, writer and director

Lena Dunham, writer and director

Neil Patrick Harris, actor

Moby, recording artist, author and activist

Michael Stipe, artist, singer/songwriter

Third Eye Blind, musicians

Kathleen Turner, actor and activist

Franchesca Ramsey, correspondent/writer on The Nightly Show

Olivia Wilde, actress, producer, director and humanitarian

Julia Stiles, actor and director

Patricia Arquette, actor and activist

Meg Ryan, actor, producer and director

Michael Mann, director

Michael Moore, director and writer

Bryan Cranston, actor

Paul Haggis, director and writer

Tony Schwartz, ghostwriter of Trump's book The Art of the Deal

Doug Liman, director

Lizzy Caplan, actor

Woody Harrelson, actor and director

Rain Phoenix, artist and activist

Jane Fonda, actor and activist

Tig Notaro, comedian and writer

Rashida Jones, actor and activist

Clea Duvall, actor

Kathryn Hahn, actor

Taylor Schilling, actor

Maggie Gyllenhaal, actor and activist

Alyssa Milano, actress, producer, humanitarian and entrepreneur

Macklemore and Ryan Lewis, musicians

Busy Phillips, actor and mother

Piper Perabo, actor

Cynthia Nixon, actor

Lea DeLaria, actor

Tamara Tunie, actor

Chloe Grace Moretz, actor

Dustin Lance Black, screenwriter

Jesse Tyler Ferguson, actor

Jill Soloway, director

Mickey Sumner, actor

Charles Ferguson, director and writer

Lesley Arfin, writer

Mary Lambert, singer-songwriter

Jesse Peretz, director

Christian Campbell, actor

Neve Campbell, actor

Talib Kweli, musician

Laura Dawn, writer, director, producer, activist

Benjamin O'Keefe, actor, writer, activist

Sarah Sophie Flicker, producer, writer, activist

Michael Skolnik, entrepreneur and activist

Paola Mendoza, director, writer and activist

Christian Siriano, fashion designer

Vanessa Hope, director

Jeffrey Marsh, Vinestar, author and LGBT activist

Diane English, writer and producer

Mara Wilson, writer

JJ Feild, actor

Kat Blaque, activist and social media influencer

Emma Myles, actor

Emily Robinson, actor

Nik Dodani, actor and comedian

Laci Green, YouTube personality and writer

Ilene Chaiken, producer

Akilah Hughes, YouTube personality

Trae Crowder, the Liberal Redneck

Mara Hoffman, designer

Rebecca Woolf, writer

Mickalene Thomas, visual artist, curator and filmmaker

Tanya Selvaratnam, artist and activist

Oskar Eustis, artistic director, The Public Theater

DJ Rekha, producer

Elizabeth Streb, director

Lucy Walker, director

Catherine Gund, filmmaker/activist

Xaviera Simmons, visual and performing artist

Chitra Ganesh, visual artist

Laura Michalchyshyn, producer

Hillary Jordan, author

Lilliana Greenfield-Sanders, filmmaker

Lisa Kron, playwright/actor

Basil Twist, puppeteer/director/designer

Dave Malloy, composer/playwright

James Tigger! Ferguson, performer and activist

Stephen Winter, filmmaker

Carlen Altman, actor, writer, activist and human

Paul Miller, aka DJ Spooky, author, musician

Jena Friedman, comedian and producer

Zoe Lister-Jones, actor, writer and director

Natalie Joos, writer, photographer and stylist

Rachel Sklar, writer

Jill Greenberg, artist

Rob Green, producer

Romy Soleimani, stylist

Lori White, writer, Upworthy

Luke Rathbone, musician

Molly R, Stern, makeup artist, designer and mother

Helen Stickler, filmmaker

India Salvor Menuez, actor and artist

Lisa Salzer, jewelry designer

Sarah Lewittin (Ultragrrrl), DJ, record producer and music critic

Hannah Rad, DJ/VJ

Marlon Taylor-Wiles, dancer/choreographer

Dita Von Teese, artist

Daron Murphy, composer and producer

Alice Roth, producer and writer

Andrew Kornhaber, producer

Eric Brown, producer

Mikki Halpin, writer, author and activist

David Ambrose, DP and producer

Isolde Brielmaier, curator and art professor

Jen Gatien, filmmaker and activist

Shruti Ganguly, filmmaker

Lisa Cortes, producer and activist

Eisa Davis, writer and performer

Joan Jonas, visual artist/performer

Leah Bonnema, comic, actor and activist

Maria Mileaf, director

Meg Thompson, literary agent

Abbi Jacobson, comic and actress

Ilana Glazer, actress