Bernie Sanders is upping the ante as he tries to close the gap with frontrunner Hillary Clinton in the race for the Democrats' 2016 White House nomination and now apparently backs an investigation into the former secretary of state's email habits, which he had previously opposed.

The Vermont senator told the Wall Street Journal that the inquiry of the security surrounding Clinton's private account is appropriate. His remarks come just weeks after he had told the audience at a Democratic presidential debate that the American people were sick of hearing about his former Senate colleague's "damn emails," Politico recalled.

Sanders insisted, however, that he did not regret his comment during the earlier encounter, suggesting that statements made in the heat of a debate are easily misinterpreted. "You get 12 seconds to say these things," he said. "There's an investigation going on right now. I did not say, 'End the investigation.' That's silly."

Even though he has attracted large crowds on the campaign trail, Sanders seemed to admit that he is still the underdog in the race, according to the Wall Street Journal.

"We had to fight very hard in the last six months to get my name out there, to get my ideas out there," Sanders said. "We still have a long way to go with the African-American community, with the Latino community....But we're working hard, and I think at the end of the day we are going to pull off one of the major political upsets in American history."

Meanwhile, Sanders attacked Clinton on the contributions she has received from financial services, which the Wall Street Journal said were among the most important donors of the former first lady and her husband, former President Bill Clinton.

"People should be suspect of candidates who receive large sums of money from Wall Street and then go out and say, 'Trust me, I'm going to really regulate Wall Street,'" Sanders challenged. "I have been walking the walk, not just talking the talk."