KEY POINTS:
The sudden expansion in the number of 2008 presidential contenders has set off a frenzied battle for campaign donations, as the United States election contest gathers steam.
US election authorities say that any top-tier would-be president will need to spend US$100 million ($145.58 million) by the end of the year to be considered a serious candidate.
Former Federal Election Commission chairman Michael Toner said campaign spending would likely approach the US$1 billion mark in 2008.
