Jason Clarke as Ted Kennedy

Kate Mara as Mary Jo Kopechne

Ed Helms as Joseph Gargan

Bruce Dern as Joseph Kennedy

Jim Gaffigan as Paul Markham

Olivia Thirlby as Rachel Schiff

Clancy Brown as Robert McNamara

Taylor Nichols as Ted Sorensen

John Fiore as Chief Arena

Gillian Mariner Gordon as Cricket

Katie Henoch as Suzy

Lexie Roth as Nance Lyons

Angela Hope Smith as Maryellen Lyons

Vincent Tycer as David Burke

Victor Warren as Stephen Smith

David De Beck as Sargent Shriver

Barry Press as Burke Marshall

Matthew Lawler as Dun Gifford

Beth Petrou as Ann Gargan

Thomas Kee as Walter Steele

Andria Blackman as Joan Kennedy

Donald Watson as Dr. Watt

Walter Driscoll as Dr. Mills

Joe Chase as John Farrar

Joseph Zamparelli as Officer Look

Charlotte Dore as Gwen Kopechne

Tim Jackson as Joseph Kopechne

Damien Di Paola as Ray LaRosa

Ed Peed as Eugene Frieh

Bill Humphreys as James Reston

Gary Tanguay as TV Interviewer

Diana Boudreau as Police Secretary

Alison Wachtler as Liz Trotta

Tony Viveiros as Floor Producer

Sean Patrick Hopkins as Ross Richards

Tamara Hickey as Marilyn Richards

Nancy O'Brien as Neighbor

Tom O'Brien as Neighbor's Husband

Noah Carpenter as Teddy Jr.

Sarah Elizabeth Mitchell as Senate Secretary

A.J. Accardi as Hotel Clerk

Theresa Curran as Cantor

Michele Proude as Vicki

Michael Fennimore as Chief of Staff

George Capaccio as Doctor

Dustin Tucker as Senatorial Aide

Jack Harte as Reporter #1

Bob Jaffe as Reporter #2

Brian Currie as Reporter #3

Paul Pape as Dick Drayne (voice)

Jake Head as James Smith (voice)

Chris Edgerly as Edmund Dinis (voice)

Wally Wingert as Newscaster (voice)

Piotr Michael as Newscaster (voice)

Bill Mootos as Older Reporter

Jody Ebling as Ethel Kennedy

Philip Dorn Hebert as Jack Crimmins

Holt Murray as Mr. Samuels

Sawyer Murray as Donnie

Rick Malone as Steele Cronie

Rick Hamilton as Ferry Captain

Caleb Enos as Deckhand

Paul Taft as Vineyard Gazette Photographer

David Callanan as Charles Tretter

Thomas Whitestone as Organist

Patrick Sheehan as Lawyer

Jeff Savage as John Culver

Tom Briody as Lawyer

David Lucas as Lawyer

Ed O'Keefe as Funeral Priest

Thomas Brogan as Edgartown Policeman

Robert Burke as Admin Worker

Charles Mathison as Admin Worker

Luke Nelson as Admin Worker

Robert Tremouille as Admin Worker

Skye Gladstone as Dike House Inhabitant

Timothy Canady as Security Agent

Patrick Parhiala as Security Agent

Whitney Cass as Security Agent

Robert Conley as Security Agent

Michael Swanson as Security Agent

Ralph Bennett as Fire Truck Driver

Nathan Bruckler as Tow Truck Driver

Camille Faman as Female Employee

Carrie Ann Quinn as RMV Attendant

Susan Garfield as Senate Staffer (uncredited)

Marinko Radakovic as Reporter

Paul Bellefeuille as Dike House Resident (uncredited)

Joe Cali as Reporter (uncredited)

Jesse Christensen as Reporter (uncredited)

Rob DiNinni as Reporter #4 (uncredited)

Stephen F Feeley as Funeral guest / mourner (uncredited)

William Galatis as Shiretown Inn Guest (uncredited)

Johnny Hawe as Stephen Sorenson (uncredited)

Bobby Kenney as Investigative News Reporter (uncredited)

Dov Kling-Levine as Protester / Local (uncredited)

Jimmy Malcolm as News Photographer (uncredited)

Jason Mulcahy as Reporter (uncredited)

Anthony Pelton as Plymouth Pennsylvania Polic Officer (uncredited)

Bill Porter as Investigative News Reporter (uncredited)

Harold Rudolph as Funeral attendee (uncredited)

John Sarnie as Mourner (uncredited)

Alexander Platt as Stan Moore

Sigrid Lium as Senate Staffer (uncredited)