Gone is the slumped shoulders, the bald head and goatee.

In his transformation from scholarly drug pin Walter White to John F Kennedy's wingman, Breaking Bad star Bryan Cranston has gained paunch, hair and presidential air.

First photos of Cranston playing Lyndon B Johnson in HBO's new biopic, All the Way, show the Emmy-award winning actor as a deal-maker of a quite different persuasion.

Cranston plays Johnson, grey haired and puffed-chested, as he takes over as America's 36th president following the assassination in Dallas of Kennedy.

Filming has begun on the drama which provides a behind-the-scenes look at Johnson's first year as America's "accidental" president, from Kennedy's assassination in November 1963 to Johnson's fight to pass the 1964 Civil Rights Act, and his own triumphant presidential campaign.

"Physically and emotionally Bryan completely channels LBJ," All the Way director Jay Roach told People.

"We just filmed him and Lady Bird in the Oval Office, after JFK's assassination. LBJ has arrived as the 'accidental President.' He's almost overwhelmed.

"In spiritual support, Lady Bird touches his cheek. We melted, like we went back in time and witnessed a private, heart-wrenching moment between these two great people."

Cranston is well-familiar with the role. At the end of six seasons playing the meth dealer White in Breaking Bad Cranston took on the role of Johnson in the same-named Broadway play.

Cranston won a Tony award for his portrayal of Johnson as a machiavellian figure who combines great moral conscience and complexity with ruthless political expediency to pass major civil rights reforms of Kennedy.

Johnson was a machiavellian manipulator and anti-hero, and so was White.

The biopic begins with JFK's assassination, says Roach.

"It covers the amazing 11-month journey from when LBJ takes office after JFK's assassination, through LBJ's fight to pass the 1964 Civil Rights Act and his own presidential campaign, culminating on the night LBJ is actually elected to the office - no longer the 'accidental President."

Pulitzer Prize winning playwright Robert Schenkkan has adapted the stage version for the small screen. Steven Spielberg will serve as executive producer on the HBO Films project, which will air in 2016.

The cast also features Anthony Mackie as Martin Luther King, Melissa Leo as Lady Bird Johnson, Bradley Whitford as Hubert Humphrey and Stephen Root as J. Edgar Hoover.