US: Former New York mayor Rudy Giuliani has taken the first step towards a presidential bid in 2008, setting up a committee to gauge the level of his support throughout the United States.
Mr Giuliani, who became a national hero in the aftermath of the 9/11 attacks, established an exploratory committee that allows him to raise funds and travel the country without formally declaring as a candidate.
"Mayor Giuliani has not made a decision yet. With the filing of this document, we have taken the necessary legal steps so an organisation can be put in place and money can be raised to explore a possible presidential run in 2008," Mr Giuliani's spokeswoman, Sunny Mindel, said.
Fellow Republican John McCain said he will take a similar step this week and California congressman Duncan Hunter has announced a bid for the Republican nomination.
Mr Giuliani's popularity could make him a formidable Republican candidate with appeal among Democrats, but his liberalism on social issues could prevent him from winning his party's nomination.
Unlike most of the conservative base that will choose the Republican nominee, he supports gun control, same-sex civil unions, embryonic stem-cell research and abortion rights. Mr Giuliani was an energetic Republican fundraiser and campaigner during the recent election campaign, making visits to states such as New Hampshire which hold early presidential primaries.
Mr McCain is a hard-line conservative on most issues, a foreign policy hawk who opposes abortion and gay rights. He remains the frontrunner to win the Republican nomination, although former Massachusetts governor Mitt Romney could be a serious rival.
On the Democratic side, former Iowa governor Tom Vilsack has formed a campaign committee and is expected to make a formal announcement of his candidacy this month.
Illinois senator Barack Obama said last month he is considering a presidential run and should decide before Christmas. He was a star attraction at many Democratic campaign events in recent weeks, and the US media are excited about his potential as a candidate.
Hillary Rodham Clinton is the Democratic favourite if she chooses to run, and her campaign could attract money and political talent more easily than most others. Other possible Democratic contenders include former vice-presidential candidate John Edwards and former Indiana governor Evan Bayh.
John Kerry's "botched joke" during the recent campaign, when he suggested that US soldiers in Iraq lacked education, has damaged his prospects for 2008. Former vice-president Al Gore was almost entirely absent from the campaign, a fact that could hinder any presidential ambitions he still nurtures.