With just over one week to go before the presidential election primaries, candidates from both parties are making a final push across the states that will vote first, all with one thought on their minds: building momentum.
Win or do better than analysts expect in three key states - Iowa, New Hampshire and South Carolina - and the campaign to become the party nominee for the Nov 8 presidential election will be on solid footing.
Do worse than expected and, for some, it could be curtains for their campaigns. "If you finish fourth or fifth in Iowa and New Hampshire, that's when you may start getting calls from your major donors," said Iowa State University's department of political science chair Mack Shelley. "They've put in all this money and will start wondering what they have to show for it."
By the end of next month, the field will likely be whittled down to only those with a serious chance of getting the nomination.
For quite different reasons, the national front runners in both parties can be quite confident of standing at the end of the first month. While both billionaire Donald Trump on the Republican side and former secretary of state Hillary Clinton on the Democratic side still have some way to go to convince their parties of their suitability, analysts generally agree these two can survive losing the early states.
TOP THREE, OR ELSE...
If you finish fourth or fifth in Iowa and New Hampshire, that's when you may start getting calls from your major donors. They've put in all this money and will start wondering what they have to show for it.
''DR MACK SHELLEY, chair of the Iowa State University department of political science.
Mr Trump is wealthy enough to self-fund, while Mrs Clinton's standing is so strong, she will remain the party favourite barring a catastrophe.
Said Dr Chris Galdieri of the New Hampshire Institute of Politics: "It would take something on the magnitude of a serious health (issue) to prevent Mrs Clinton from winning the nomination. (Senator Bernie) Sanders doesn't have the establishment backing and is too much of an outsider."
Still, both Mr Trump and Mrs Clinton have seen their competitors either catch up or overtake them in polls in recent weeks.
For the Republicans, an average of polls done by website RealClearPolitics shows Mr Trump with a 2.6 percentage point lead in Iowa over second-placed Senator Ted Cruz. Mr Trump, in fact, leads in every poll for the early states.
Yet, Mr Cruz is now favourite to win Iowa. Though Mr Trump is ahead among all likely primary voters there, Mr Cruz leads among those who have actually voted before. Iowa Republicans are primarily evangelical Christians, which gives Mr Cruz, son of a conservative evangelical pastor, an edge.
On the other hand, experts are unclear if Mr Trump's supporters will be committed enough to turn up and vote for him, since the voting process there takes up to three hours. The Iowa caucus is like a town hall and includes a discussion of issues and the election of members of various committees.
The results will thus give the first real indication of how seriously to take the Trump candidacy.
Third place will also be closely watched as it gives the first hint of who among the establishment Republicans now lagging behind - Senator Marco Rubio, governors Chris Christie and John Kasich, and former governor Jeb Bush - might be able to make a breakthrough.
"If you finish in the top three, you are pretty much able to live to fight another day," said Dr Shelley.
As for the Democrats, Mrs Clinton and Mr Sanders have mixed fortunes. Mr Sanders leads in New Hampshire, a state next to his home state Vermont and which has a history of favouring the independentminded, but trails in the other two.
Mrs Clinton is especially strong in South Carolina where the Democratic caucus voters are predominantly black. Her husband Bill Clinton's civil rights record while president (1993-2001) is a plus for her with the black community. She is projected to win in South Carolina while expected to lose New Hampshire.
It is Iowa that appears to be a toss-up because Mrs Clinton has a small lead and Mr Sanders has been gaining momentum.
That said, observers caution that early primary polls are not always accurate indicators of what would come.
Said Professor Neil Malhotra of Stanford University: "Part of the problem is that it's not easy to predict how people will vote in primaries... People aren't paying very close attention to politics and you don't have the party label to make a decision on."