The rivalry between Hillary Rodham Clinton and Bernie Sanders, her prime challenger, will be at forefront in the Democrats debate, the first of six planned debates of the 2016 campaign. Both will take part in the debate on Tuesday in Las Vegas.
Clinton, the Democratic front-runner, said that she always expected tough competition in the Democratic presidential primary. However, she did not expect that Sanders, independent senator from Vermont, would be her rivalry.
The senator and the former secretary of state will be joined by former Maryland Governor Martin O'Malley, former Rhode Island Governor Lincoln Chafee and former US Senator Jim Webb of Virginia.
Clinton and Sanders have avoided personal attacks for months. However in recent days, their attitudes have shown that they began to jab at each other.
Sanders, a self-described socialist, warned the party’s left wing and filled areas with big crowds stating a persistent message of eradicating income equality and reining in Wall Street.
In response, Clinton changed her stances on key issues that align her with Sanders. She announced her opposition to the 12-nation Trans-Pacific Partnership trade deal (TPP) and rejected the Keystone XL oil pipeline that she intended to approve in 2010.
Sanders said that he would mention Clinton’s tardiness on those issues in the debate, saying that he was glad Clinton had reached that conclusion and noted that he opposed Keystone and the TPP "from day one."
Labor leaders praised Clinton for her opposition to the TPP. Labor has also opposed the TPP saying that the pact would cost manufacturing jobs and weaken environmental laws.
"I don't think she ever had any inclination to back TPP," said R. Thomas Buffenbarger, a Clinton ally who is president of the International Association of Machinists and Aerospace Workers, which has supported Clinton.
Clinton has moved to the left on her domestic policy since this spring including showing support for expansive gun control legislation and opposition to the Keystone XL oil pipeline. She states that her proposals are more realistic and well-formed than those by Sanders.
In an interview last week, Clinton criticised Sanders’ call for free college tuition saying that “I'm a little different from those who say 'free college for everybody. I am not in favor of making college free for Donald Trump's kids."
The debate would be a welcome reprieve from the months of focus about her use of a private email server instead of a government account during her time as secretary of state. The allegations overshadowed her presidential campaign and caused a fall from her voters’ grace.
Former Maryland Governor Martin O'Malley who wants to be Clinton’s primary rival has been criticised what he described as Clinton’s flip-flopping on policy and said her usage of private email are legitimate.
Democratic strategist Jim Manley said he expected O’Malley to push Clinton in the debate because his last chance to draw attention for his campaign.
"This is a chance for him to establish a rationale for his candidacy, which so far has been missing," Manley said.
Some policy differences are still controversial between Sanders and Clinton. Sanders voted against the 1993 Brady handgun bill that President Bill Clinton signed into law and called for his "sensible approach" on gun control.
Clinton supported to back a no-fly zone in Syria to give refugees a safe corridor, which separated Clinton from the White House on the issue as Sanders believed it could be a step toward pulling the United States into the Syrian civil war.
Sanders dissuaded Super PACs from raising funds on his behalf, pointing out the influence of corporate money. Several Super PACs supports Clinton.
Eric Davis, a professor emeritus of political science at Middlebury College in Vermont, said that he expected Sanders "to have a vigorous critique of Hillary Clinton on things like campaign finance," and he could criticise Clinton for "the way she is financing her campaign and her perceived closeness to Wall Street interests."
Lincoln Chafee, the Republican-turned independent-turned Democrat and former Virginia Senator Jim Webb, a decorated Vietnam veteran will also take stage in the debate.
Webb criticised Clinton for her early support of the Iraq war and could be aggressive to Clinton for her foreign policy positions on Tuesday’s debate.
Meanwhile, Chafee’s most notable campaign moment was that he called for the US to adopt the metric system.