UPDATE 2-Obama, Huckabee leading in Iowa poll

(Adds Clinton campaign reaction, paragraphs 12-13)

By Deborah Charles

DES MOINES, Iowa, Dec 31 (Reuters) - Democratic presidential candidate Barack Obama has widened his lead in Iowa over rivals Hillary Clinton and John Edwards heading into Thursday's caucuses, according to a poll by The Des Moines Register released on Monday.

Obama, an Illinois senator, was the choice of 32 percent of likely Democratic caucus-goers, up from 28 percent in the Register's previous poll in late November, the newspaper reported.

Clinton, a New York senator and former first lady, held steady at 25 percent and Edwards, a former North Carolina senator, was also steady at 24 percent, the paper said.

No other Democrat received support from more than 6 percent of likely caucus participants, according to the poll.

In the Republican race, Mike Huckabee, a former Arkansas governor, maintained his lead over former Massachusetts Gov. Mitt Romney, 32 percent to 26 percent, the poll found.

Huckabee's lead was virtually unchanged from the previous Iowa poll taken in late November, despite Romney's hard-charging effort to regain the top spot he held earlier in the year, the newspaper said.

Arizona Sen. John McCain was in third place in the Republican race with 13 percent support in the poll, up 6 points since late November, the newspaper said.