Six Things to Watch for in Tonight's Caucus....

1. Ron Paul

The Republican congressman who favors an immediate pullout from Iraq and an end to income tax claims he is written off by the US media as an eccentric. But he has build up a fervent base of support who helped him make political history last month by raising $6m in 24 hours through the internet. Could he make third place?

2. Democrats' second choice

Democratic party rules call for a second round of voting in which those who have backed trailing candidates can transfer their support to those in the lead. In a tight race, will that second round of voting make all the difference?

3. John McCain

He largely bypassed the state, focusing his campaign on New Hampshire, but he did make a quick trip to Iowa on Wednesday night. A rally at his Des Moines headquarters was so crowded they had to turn people away. How well will he do?

4. First time voters

A number of candidates are counting on support from first time caucus goers to put them in the lead. Barack Obama is hoping for a big turnout of younger people as well as non-aligned voters. Hillary Clinton has been targeting middle-aged women who vote, but have never caucused.

5. The weather

Thursday's forecast is for temperatures to climb several degrees to a relatively balmy -3C, which could drive up turnout.

6. Abandoned gifts

How fast will the election paraphernalia disappear from Iowa? With blizzards expected before the winter is over, the posters are unlikely to last long. The badges, car stickers and the fridge magnets are also likely to have a short life. The mugs given away or sold by almost all the candidates should survive a few years, albeit becoming increasingly chipped. But the best chance of longevity is likely to be the snow shovels given away by the Clinton campaign.