In the first contest in the 2016 Republican presidential campaign, voters in Iowa will gather in caucuses across the state and decide who they want to be the nominee.

Here is my assessment of where the campaigns are - and where they're headed.

JEB BUSH: Bush has seen his popularity fall spectacularly in recent months and has spent millions in Iowa only to witness his poll numbers plummet. The former Florida governor continues to believe voters will eventually turn from the Donald Trump sideshow and vote sensibly, by which he means him. He needs a solid performance in Iowa and to do well in New Hampshire a week later or his campaign is over.

BEN CARSON: Carson has had to shake up his campaign team and his own performance but continues to pull good crowds wherever he goes. A former neurosurgeon with no experience in political office, he struggles on foreign policy issues, but that's not a major concern in Iowa. He is looking at a top-four finish, which will be enough to keep his campaign rolling on for a while yet. 

CHRIS CHRISTIE: Christie is almost ignoring Iowa - preferring to concentrate his efforts in New Hampshire.  And he's seeing his numbers rise, although he remains behind Trump. He needs a top-three finish in New Hampshire - or the New Jersey governor is finished.

TED CRUZ: Four years ago in Iowa, the name we kept hearing among voters was Rick Santorum, who was polling in single figures. He went on to win the caucus. That's where Ted Cruz is this time around, and the Texas senator stands a good chance of winning the state. Strong with evangelical voters, strong with conservatives, he is the sort of candidate Iowans like. He won't do so well in New Hampshire, but a good performance in the third contest in South Carolina could put him well on the well to the nomination.

CARLY FIORINA: Fiorina had her big moment when she moved up from the undercard debate on to the main stage at the second Republican debate. If she's not in the top five in Iowa, and that seems unlikely, she'll be under pressure to drop out.


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MIKE HUCKERBEE: Huckerbee has completed the tour of all 99 counties in Iowa and believes he can still win, but it would take a remarkable surge in the polls to do so. He could take support from Ted Cruz, which is a worry for his campaign. A former Arkansas governor, he won the state in the 2008 nominating contest but that was really the high point of his campaign. He says if he doesn't come in the top three he will drop out.  He won't be booking hotels in New Hampshire.

JOHN KASICH: Like Christie, Kasich is pushing on with a one-state strategy knowing Iowa is unlikely to be fertile ground for him. While many Republicans tell me they like him, they say they won't vote for him. He really believes he is best qualified to be president but after New Hampshire, it's likely he’ll have to head back and content himself being governor of Ohio.

RAND PAUL:  Paul won't win Iowa, won't win New Hampshire, won't win South Carolina, so why is the Kentucky senator staying in the race? He's spent a lot of time, effort and money organising in western states. If he doesn't win Nevada or Colorado in March, he'll be done.

MARCO RUBIO: Rubio is thought of as everyone's second-favourite Republican. He is looking at a top-four finish in Iowa. From there he has to win New Hampshire or there's no real road to the nomination for the Florida senator. He's currently sitting second there, but things could change on the back of Iowa's result. 


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RICK SANTORUM: Santorium still believes he can catch lightning in a bottle and win Iowa again. He has been consistently polling in single figures, but while four years ago he was the one everyone was talking about, most people forget he's even in the race now. An early Iowa casualty.

DONALD TRUMP:  The biggest question over Trump in Iowa is has he spent enough time and effort organising support on the ground? He has had the media coverage, he is now spending on TV ads, but he actually needs to get people to caucus for him. If he doesn't win then the bubble might finally burst. How can you tell people you'll be the "most winningest" president ever but lose your first real contest? And if he doesn't win Iowa, his support in New Hampshire might shift elsewhere (see Rubio above). The billionaire businessman needs a win or the game changes.