The Prospects of the front-runners in the race to the White House could be boosted or busted by the outcome of the first of the primaries, in Iowa, in February – in which Hillary Clinton and Donald Trump are the current favourites to emerge as the top choice for their respective Parties.
Ms Clinton is 8/15 favourite with William Hill in the Democrat contest, ahead of 11/8 chance Bernie Sanders and 66/1 shot Martin O'Malley.
Mr Trump is also odds-on favourite, at 8/11 to come out top of the Republicans, ahead of Even money chance Ted Cruz; 14/1 Marco Rubio and 40/1 Ben Carson.
'Momentum is an important factor in a long-term contest of this nature, and whoever comes out on top in Iowa will be off to a flying start, and receive a huge boost to their campaigns.' said William Hill spokesman Graham Sharpe.
To Be President... 8/11 Clinton; 10/3 Trump; 6/1 Sanders; 6/1 Rubio; 16/1 Cruz; 22/1 Jeb Bush; 40/1 Chris Christie.