Democratic US Presidential hopefuls Barack Obama and John Edwards surged ahead of Hillary Clinton during the overnight hours in what could be a devastating blow to the Clinton campaign in Iowa come Thursday night when the final Caucus tallies are in. Barack Obama was now leading by 4% in a Reuters/C-SPAN/Zogby poll released on Thursday. Edwards had passed by Clinton.

Obama was at 31 percent among likely Democratic caucus-goers, Edwards at 27 percent and Clinton 24 percent. No other Democrat was in double digits.

On the Republican front, Mike Huckabee expanded his lead to six points, 31 to 25 percent, over former Massachusetts Gov. Mitt Romney while third place is essentially up for grabs.

The poll had Former Tennessee Sen. Fred Thompson is in third place in the Republican race at 11 percent and Arizona Sen. John McCain slipped two points to 10 percent. Texas Rep. Ron Paul also registered 10 percent. The Ron Paul camp believes that their candidate will rank a few percentage points above any official polling numbers, more towards the upper end of the 3 percent margin of error, since many of his supporters have never voted before and are less inclined to have land line phones.

About 6 percent of Republicans and 5 percent of Democrats remain undecided, leaving room for late swings.

The rolling poll of 905 likely Democratic caucus-goers and 914 likely Republican caucus-goers was taken Sunday through Wednesday.

Online gambling website, Bookmaker.com, mirrored the Reuters Poll but with Clinton slightly ahead of Edwards while Romney and Huckabee were more neck and neck.