US presidential hopeful Martin O'Malley is stressing his relative youth as he prepares to challenge the perception that Hillary Clinton's campaign to become the Democratic nominee is unstoppable. In an interview with The Irish Times, the Irish-American former Baltimore mayor and former Maryland governor, who is due to announce his candidacy on Saturday, said he had a tremendous amount of respect and admiration for the frontrunner.

"But an election, especially an election as important as the election of the next president of the United States, is not about what's good for the Clintons or for that matter what's good for the O'Malleys. It's about what's good for our country," he said.

Mr O’Malley (52) is regarded as having positioned himself to the left of Ms Clinton (67) in order to appeal to the Democrats’ progressive base. “I don’t see myself as to the left or right of the other candidates in the party. I see myself as forward of them. I’m younger than they are. I therefore arrive at some conclusions on important issues in advance of the other candidates.”

Asked about the widely held belief, backed up by polling, that Ms Clinton’s candidacy is unstoppable within the Democratic Party, he said: “Every year there’s an unstoppable candidacy. Inevitable frontrunners are inevitable right up until they’re no longer inevitable.”

He said the Republican Party tended to "retread old names" while the Democrats tended to look to the future more. "In our party, there usually emerges a choice between the candidate that everybody knows and the new candidate of a new generation that none of us has ever really heard of much," he said.

Mr O'Malley said his paternal great-grandfather left the Maam Valley in Connemara in the 1880s. He is related to Aidan Gavin, managing director of DTZ Sherry FitzGerald, and addressed an event in Dún Laoghaire yacht club on Sunday which was organised by business consultant Ronan King.

Sherry FitzGerald contributed to Mr O’Malley’s travel costs and invited guests including former minister for education Ruairí Quinn and senior businesspeople. His trip to Dublin was rescheduled from last month when he cancelled a visit due to civil unrest in Baltimore.

Fans of the American television series The Wire, which is set in the city of Baltimore, will know Mr O'Malley was the inspiration for the crime-busting mayor character Tommy Carcetti (played by Irish actor Aidan Gillen).

The writer and creator of the acclaimed drama David Simon recently criticised Mr O'Malley and suggested policies implemented during his 1999 to 2007 tenure as mayor of the city created a situation which led to tensions boiling over. He claimed Mr O'Malley's adoption of a so-called zero-tolerance approach involved manipulating statistics to show a sharp drop in crime levels and created a police culture of mass arrests.

Responding to Mr Simon’s criticisms, Mr O’Malley said: “I didn’t have the luxury of being able to hold on to an ideology when I was elected mayor. I had to save lives and turn my city around. So I did the things that worked.”

Turning to US foreign policy, he said a more collaborative approach should be crafted with like-minded people around the world. “A fresh perspective is needed to construct a national security strategy that makes a break with the old cold war way of looking at the world and instead puts the reduction of threats at the centre of the matrix hereand is willing to join and form new alliances in order to mitigate these threats before the only options left to us are military.”

Mr O’Malley, who led the passage of same-sex marriage legislation as governor in Maryland by popular vote in 2012, welcomed the Irish Yes vote in the referendum at the weekend. He said Irish people had never been threatened by other cultures. “This is the country you’ve always been,” he said.

Mr O’Malley said the challenges of the second decade of the 21st century were very different from those of the last decade of the 20th century. “Times change and new times require new thinking and new perspective and new questions too,” he said.

“It’s been my experience in helping and mentoring and sharing best practices with other mayors and other governors that new leaders have a lot easier time embracing new ways than old leaders who oftentimes feel that they have to defend old decisions or old legacies rather than being open to new possibilities.

“That’s been my experience with mayors and governors.”