DES MOINES, Iowa (CNN) -- After most took Christmas Day off the campaign trail, presidential candidates are flocking back to Iowa to try to break the logjam at the top of the Hawkeye State's first-in-the-nation caucus.
The Democratic race for the January 3 caucus remains a three-way dead heat between Sens. Hillary Clinton of New York and Barack Obama of Illinois and former Sen. John Edwards of North Carolina.
On the Republican side, former Arkansas Gov. Mike Huckabee's recent poll surge puts him ahead of former Massachusetts Gov. Mitt Romney.
But more voters haven't yet made up their minds -- one in three likely Democratic caucus-goers said they're still trying to decide whom to support. And 40 percent of Republican caucus-goers also said they're undecided, according to a CNN/Opinion Research Corp. poll released last week.
Keating Holland, CNN's polling director, warned that "all these figures should be treated with extra caution, because it is extraordinarily difficult for polls to accurately assess who will attend the caucuses, and Iowans are notorious for making their minds up late in the game."
Romney was stung by hostile editorials in two of the Granite State's leading newspapers over the past few days. Watch how Romney's numbers have cooled »
The Concord Monitor printed an editorial on Sunday calling Romney "a disquieting figure who sure looks like the next president and most surely must be stopped."
And Wednesday's Manchester Union-Leader, which has endorsed Republican rival Sen. John McCain of Arizona, editorialized that "the more Mitt Romney speaks, the less believable he becomes."
In Iowa, Romney has launched a barrage of ads attacking Huckabee on immigration and taxes, trying to stall his surge there. According to the American Research Group poll, it might be working -- Huckabee held an 11-point lead over Romney last week, but the Christmas Eve survey said the two were in a statistical tie. Watch Republicans' strategy for Iowa »
Meanwhile, McCain has surged back into the Iowa race -- a CNN poll last week showed the senator with 9 percent of the GOP vote, but the American Research Group survey found him a few percentage points behind Huckabee and Romney.
McCain also picked up a key newspaper endorsement in Iowa when The Des Moines Register, the state's leading paper, editorialized that he was the best choice among GOP candidates.
Among the Democrats, Clinton's campaign is looking past her opponents in Iowa and toward the general election on her "Big Challenges, Real Solutions -- Time to Pick a President" tour. The former first lady ranks highest in most polls in her electability against Republicans. Watch Democrats' strategy for Iowa »
Obama is focusing on rural voters, where Edwards appears strongest, according to polls, on a Wednesday bus tour. E-mail to a friend
CNN's Dana Bash, Bill Schneider and Jessica Yellin contributed to this report.