WASHINGTON, Dec. 5 (Xinhua) -- Former U.S. Secretary of State John Kerry on Thursday endorsed former U.S. Vice President Joe Biden's presidential bid.
"I'm not endorsing Joe because I've known him for so long, but because I know him so well," Kerry tweeted. "He'll be ready on day one to put back together the country and the world that (U.S. President) Donald Trump has broken apart."
As the 2004 Democratic nominee for the White House and a five-term senator representing Massachusetts, Kerry will join Biden for campaign stops in coming days, according to the former vice president's team.
Biden, 77, served as vice president from 2009 to 2017 to then President Barack Obama. Kerry was the Obama administration's secretary of state from 2013 to 2017.
During a town hall event in Iowa on Thursday, Biden engaged in a testy exchange with a voter questioning his age and his son's dealings in Ukraine.
Biden told the voter "No one has said my son has done anything wrong and I did not on any occasion."
He also responded by challenging the voter to a pushup match, a running competition and an IQ test.
Biden formally announced his bid for the Democratic nomination for U.S. presidency in April and has campaigned as a moderate and on his political experiences.
According to the latest RealClearPolitics national Democratic primary polling average, Biden is leading a 15-member field at 27.8 percent, followed by progressive Senators Bernie Sanders and Elizabeth Warren.
