WASHINGTON • After ignoring her chief rival for months, White House contender Hillary Clinton is at last confronting independent Senator Bernie Sanders.
Mrs Clinton faces Mr Sanders and three other hopefuls in the first Democratic debate of the 2016 primary contest, to be held in Las Vegas last night.
While a dramatic clash of personalities as seen in the first two Republican debates seemed unlikely, the spotlight is certain to concentrate on the top two candidates.
The other three challengers - former Maryland governor Martin O'Malley, ex-senator Jim Webb and former Rhode Island governor Lincoln Chafee - are struggling to gain traction in the race for the Democratic nomination, so the debate offers them mainly a chance to show they are electable alternatives to Mrs Clinton.
United States Vice-President Joe Biden has been mulling a run for months, but he has not announced his decision.
Mrs Clinton is nearly eight years past her previous campaign clashes, when she sought the 2008 nomination but lost out to ultimate White House winner Barack Obama.
Along with focusing on her recently unveiled proposals on gun control, Wall Street regulations and other policies, Mrs Clinton has to prove to voters that she is the candidate to beat despite her numbers trending downwards in recent months.
Mrs Clinton still leads nationally in polls, but she trails Mr Sanders by nearly 10 points in New Hampshire and holds only a modest lead in Iowa, both key early-voting states.
Her lead increases in debate state Nevada, where her support has reached 50 per cent compared with 34 per cent for Mr Sanders and 12 per cent for Mr Biden, according to a CNN/ORC poll released on Monday.
Mr Sanders, a rumpled, self-declared democratic socialist, has drawn huge campaign crowds, but the debate is the biggest test of his decades-long political career as he seeks to build national support.
While Mr Sanders said in advance that he was unlikely to level "personal attacks", he suggested that he will try to hit Mrs Clinton on her recent position shifts, including her opposition to the Canada-to-US Keystone oil pipeline and her criticism of the huge Trans Pacific Partnership (TPP) trade deal that she supported on multiple trips to Asia.
"People will have to contrast my consistency and my willingness to stand up to Wall Street and corporations with the secretary," Mr Sanders told NBC on Sunday.
The Sanders campaign showed another line of attack over the weekend by releasing a statement outlining Mr Sanders' 2002 vote against authorising the use of force in Iraq sought by President George Bush - which Mrs Clinton voted for.
Mr Obama opposed the war, and his difference with Mrs Clinton on the matter marked a defining issue in their 2008 showdown.
She has since acknowledged she was wrong to cast that vote.
Mrs Clinton was thought likely to use her rival's moderate position on guns to highlight an area where liberals, who seek tighter gun laws, break with Mr Sanders.
Mr Sanders casts himself as the anti-billionaire candidate intent on reshaping an economic system he says rewards the wealthiest Americans while leaving millions in poverty.