Joe Biden: ‘I Would Have Been the Best President’ Biden’s decision not to run was viewed as a boost to Hillary Clinton’s bid.

 -- Vice President Joe Biden says he “would have been the best president” if he had mounted a successful campaign in the 2016 election, but that forgoing the race was the right decision for his family.

Speaking with “Good Morning America” co-anchor Robin Roberts in an exclusive interview that aired today, Biden said he had planned to run but changed course only after his eldest son Beau died last May.

“No one should ever seek the presidency unless they're able to devote their whole heart and soul and passion into just doing that,” he said. “And, Beau was my soul. I just wasn't ready to be able to do that. But, so, my one regret is my Beau's not here. I don't have any other regrets.”

For months last year the question of whether Biden would run loomed over the Democratic presidential contest. Then in October he announced that he and his family were still dealing with the grief over Beau’s death and he would not seek the presidency.

Beau Biden died in May 2015 at the age of 46 after a battling brain cancer for years.

The vice president’s comments came during an interview with Roberts about his “Cancer Moon Shot” initiative, which aims to accelerate the effort to improve treatments for cancer and to possibly find a cure.

“It's kind of bittersweet,” Biden told Roberts of his role leading the administration’s fight against the disease that took his son. “But this is -- this allows me to pour all my energies into -- doing somethin' that -- hopefully will -- five years from now if -- someone's diagnosed with what my Beau was diagnosed with, they -- they live.”

His decision last year not to run was viewed as a boost to Hillary Clinton’s run for the Democratic Party’s nomination.

Biden has not endorsed either Clinton or Sen. Bernie Sanders, her opponent in the primary, but he said he thinks Clinton will be the nominee.

“I feel confident that Hillary will be the nominee," Biden said, "and I feel confident she’ll be the next president."