Iowa first step to next president

By John Whitesides, Political Correspondent

DES MOINES, Iowa (Reuters) - Voters in Iowa begin the process of choosing the next U.S. president on Thursday, and a new poll showed Barack Obama leading John Edwards in the Democratic nominating contest -- with Hillary Clinton falling to a potentially disastrous third.

The Reuters/C-SPAN/Zogby poll also showed Republican Mike Huckabee expanding his lead on rival Mitt Romney as the most heavily contested presidential caucus in Iowa history draws to a close.

For the winner in Iowa, the prize is a valuable shot of momentum and at least a temporary claim to the front-runner's slot in their party's nomination battle.

The third-place finisher in the heavyweight Democratic showdown, meanwhile, could find themselves severely wounded heading into the next contest in New Hampshire on Tuesday.

The final Reuters/C-SPAN/Zogby tracking poll before Iowa's caucus on Thursday showed Obama surging to a four-point lead over Edwards at 31 percent to 27 percent. Clinton fell to third place at 24 percent.

For Clinton, who a few months ago was declared in some quarters the almost certain Democratic nominee, a third-place finish in Iowa would be a heavy blow and would create immense pressure for a win in New Hampshire next Tuesday.

Huckabee, the former Arkansas governor whose bare-bones campaign has steadily climbed since a second-place finish at the Iowa straw poll in August, expanded his lead over Romney in the Republican race to 31 percent to 25 percent.

He took a brief break from frigid Iowa to fly to California and appear on "The Tonight Show" with Jay Leno, playing bass with the house band and crossing a picket line to appear on the show while expressing support for striking writers.