South Carolina is bringing forward its Republican presidential primary poll, a move set to trigger further changes in the US electoral calendar.
Candidates' campaigns are already in full swing
The primary, originally set for 2 February, will be held on 19 January, the state's Republican chairman said.
In a presidential election year, states hold primaries and caucuses to choose Democratic and Republican nominees.
Candidates who do not do well in early elections tend to drop out, so giving those states who decide first more say.
The changing electoral schedule is proving a stiff test for the candidates as their campaigns have to decide which states to focus their energy - and their money - on.
Some states get the electoral ball rolling with primaries - an election where voters indicate a preference for a candidate - while others use caucuses - party meetings to endorse candidates.
CURRENT KEY DATES
14 Jan: Iowa caucus
19 Jan: South Carolina primary
22 Jan: New Hampshire primary
29 Jan: Florida
5 Feb: some 20 states including California, New York, New Jersey
Larger states like California and Florida, who previously held their primaries later on in the process, have now moved their elections forward.
Florida is due to hold its primary on 29 January, while California joins a raft of other states holding their elections on 5 February 2008, which has already been dubbed "Super-Duper Tuesday".
South Carolina Republican Party Chairman Katon Dawson announced the date change in Concord, New Hampshire alongside New Hampshire officials.
"We are here to stand shoulder to shoulder with our friends in New Hampshire to reaffirm the important role that both our states play in presidential politics," Mr Dawson said.
Campaigning in person is crucial in key states
The change was needed, Mr Dawson said, to protect South Carolina's tradition of being the first Southern state to hold a primary.
South Carolina Democrats have already said they will stay with their original date of 29 January for their primary.
The Republicans' decision, however, has implications for New Hampshire, which has a state law determining that its primary be held at least a week before any other state's.
This means the New Hampshire Secretary of State William Gardner will have to move the primary forward to at least 12 January.
The shifting dates will also have an effect on Iowa, which has a state law that it must be the first to hold any kind of voting procedure.
That means the Iowa caucuses must come before the New Hampshire primary in the electoral calendar.
The Iowa caucus is currently set for 14 January but the changes could mean Iowa officials having to decide whether to set the caucus for around the New Year period, or even bring it forward to December this year.