'House of Cards': How far does Doug Stamper's loyalty go

— -- For the past four years, actor Michael Kelly has portrayed Doug Stamper, Frank Underwood's chief of staff, loyal friend and sometime assassin, on the Netflix drama "House of Cards."

It's a role that Kelly, 49, relishes.

"As an actor to get to play someone so complicated -- I always say he’s not really a bad guy. He just does some bad things," Kelly told ABC News.

"Like every season, the guy goes through hell," Kelly added. "Everything is put on his plate. He's either devouring it or throwing it away. He's always doing these Machiavellian deeds to do what he thinks is the right thing. It’s all about the job."

In past seasons, that job has required Stamper to go to extremes, including murder. In season 5, which debuted May 30, Kelly finds his loyalty to President Underwood, played by Kevin Spacey, tested.

"Doug proves he’s the ultimate. He goes as far as he’s ever gone," Kelly said.

Kelly described Stamper's relationship with Underwood as "the closest thing to a friend that Doug has in his life."

"To play a character who doesn’t have a friend, what does that say about this guy?" he continued. "It’s just odd to think of a man without a friend."

He went on, "That loyalty to Frank is a byproduct of his loyalty to his job. He’s loyal to his job."

Is there no limit to Doug's loyalty?

"Obviously if Frank were to turn on him, sure," Kelly said. "I think about that -- and I think Doug would just walk away. He’s not going to go seek revenge."

This season, the Netflix drama has drawn comparisons to the real political drama currently unfolding in Washington, D.C.

Robin Wright, who plays first lady and vice-presidential candidate Claire Underwood, joked at Cannes last month that "Trump has stolen all of our ideas for season 6."

Given the choice, Kelly is clear about which president he'd rather have in office -- Frank Underwood or Donald Trump.

"Frank," Kelly said without any hesitation. "I know the man has killed someone, as he’s make-believe, but I'd rather have Kevin Spacey play the president ... I'd rather have my 4-and-a-half-year-old be the president."

All 13 episodes of season 5 are currently on Netflix.