Farcical candidates like Donald Trump and Herman Cain have made this one of the weirdest political contests in history, but they are a thing of the past as we look at the six principal candidates.

Despite long standing concerns about his Conservative credentials and authenticity amongst the Republican base, Romney remains a red-hot 1.7 favourite to win his party's nomination. The billionaire former Massachuesetts Governor has more campaign resources than all his rivals combined, and is usually presented as the candidate most likely to beat Obama. A weekend endorsement by Iowa's biggest newspaper, the Des Moines Register, served to cement his status as the front-runner and establishment pick.

Whether that is enough remains to be seen. In the two months since I recommended laying Romney for the Presidency, Republican voters have flirted with numerous alternatives, and the latest nationwide poll of them shows him stalled at just 24%. For the front-runner, most heavily touted candidate, well known from a failed run four years ago, that is a diabolical rating at this relatively early stage, raising big doubts that he could survive a united 'anti-Romney' campaign once lesser candidates have been whittled away. After all, Romney's rivals know his weaknesses and how to exploit them, whether it's his flip-flopping reputation, Mormon faith, or corporate past. 

Romney needs a win in Iowa to quell doubts and more importantly, puncture the momentum of others. While nobody would turn their nose up at an endorsement, that Iowa newspaper's failure to back a primary winner since 2000 doesn't bode well. Nevertheless, he must be heartened by a surprise lead in the latest poll for this key opening state, after weeks of trailing badly.

The latest 'Anyone but Mitt' candidate has no shortage of political baggage or enemies, is hampered by a lack of resources, but may well have the necessary staying power. Gingrich is apparently hated by much of the Republican establishment, from his days as House Speaker during the 1990s, which may also prove a huge disadvantage in any subsequent contest against Obama. Nevertheless, much of the Tea Party have warmed to his candidacy, and right now he holds a consistent lead in nationwide Republican polls. Significantly, that support tends to come from older voters and strong Republican identifiers, who reliably turn out in big numbers.

Iowa is pivotal for Gingrich, as victory there will cement his position ahead of other early favourable primaries such as South Carolina and Florida, and help see off potential rivals for Tea Party support. Those weaknesses may not be such a disaster if history is a guide. Four years ago, John McCain had even less cash and similar problems with the party hierachy, yet swept to the nomination with ease.

Driven particularly by young, internet savvy activists, the Texan Congressman is the latest flavour of the month. Paul's emergence, despite miniscule media coverage, is the reason for Gingrich's Iowa lead evaporating in recent days. The question now is whether, like others before him, the scrutiny that comes with contention will swiftly put paid to his chance. As his rivals have been swift to point out, Paul's isolationist foreign policy stance and views of recent wars may be too much for the Republican base to swallow. Is the same electorate that picked George W Bush and military hero John '1000 Years in Iraq' McCain really going to choose a man who said "The only weapon of mass destruction in Iraq is the US military"? 

The best thing that could be said of Perry's campaign is that, unlike Donald Trump or Herman Cain, at least he's still in the race. When the Texas Governor announced his candidacy, punters reacted favourably, backing him down to 2.22 favourite. Then came a plethora of gaffes, most famously this widely mocked 'Oops' moment. Nevertheless, while Perry is now an outsider, he has plenty of cash behind him and if Gingrich were to falter, could plausibly survive as the last anti-Romney candidate. No wonder he's upped the rhetoric in recent days, attacking Romney for being 'part of Wall Street'.

Perhaps not surprisingly given his moderate views on healthcare, immigration and gay marriage, the former diplomat and Utah Governor has yet to make any impact on the race and is polling at just 2% nationwide. There's only room for one moderate in any modern Republican race, and much as the definition might annoy Liberals, Romney has that market sewn up. 

Bachmann has no hope whatsoever of becoming President or even winning the nomination, but her extreme views have a significant loyal following, and her presence undermines other Tea Party favourites. Indeed, it was Bachmann's early impact that put paid to the much-fancied Tim Pawlenty. Her recent war of words with Paul over Muslims has probably raised both their profiles - which is bad news for Gingrich and Perry.