US Senator Tim Kaine of Virginia has endorsed Hillary Rodham Clinton for president, even though the former secretary of state has not announced if she will seek the White House in 2016.
Kaine, who backed Barack Obama when he beat Clinton for the Democratic presidential nomination in 2008, announced his support on Twitter and at a breakfast meeting of the South Carolina Women's Democratic Council in Columbia, South Carolina, on Saturday.
"Today I encouraged Hillary Clinton to run for president & pledged my support for her candidacy if she does," Kaine said in a tweet that linked to his earlier remarks on www.readyforhillary.com , the website of one of the most prominent and vocal pro-Clinton organisations.
"She understands the challenges facing Americans from all walks of life and has the compassion and skill necessary to help improve our everyday lives," said Kaine, who was governor of Virginia from 2006 to 2010.
Kaine added that Clinton's work as secretary of state, senator from New York and first lady during her husband Bill Clinton's presidency also give her a deep background on foreign policy.
Polls taken this year show Clinton with an advantage of more than 50 percentage points over other potential Democratic candidates, including Vice-President Joe Biden.
Clinton said in April she was thinking about running in 2016 and was "going to continue to think about it for a while".