MARSHALLTOWN, Iowa - In a final day of campaigning before suspending their campaigns for Christmas, Sen. Hillary Rodham Clinton, D-N.Y., encouraged voters here to view the holiday as a time to become "instruments of peace and change," while Sen. Barack Obama, D-Ill., accused former Sen. John Edwards, D-N.C., of using outside groups to shape an intense three-way race.

Obama continued his attempt to undercut Edwards over the use of independent "527" groups that are playing an increasing role in the campaign.

Such outside Democratic groups are backing Edwards and Clinton and have purchased sizable blocks of broadcast advertising in the early voting states, including Iowa.

Obama criticized Edwards for one such group that is running ads on his behalf and is being operated, in part, by his former campaign manager and political director. By law, Edwards cannot coordinate with the group, but Obama said Edwards should block the group from participating in the process.

"My attitude is that if you can't get your former campaign manager and political director to do what you'd like, then it's going to be hard to get the insurance companies and drug companies to do what you want," Obama said.

Edwards aides struck back by noting that Edwards, not Obama, has never taken money from lobbyists or PACs.

"John Edwards is the only candidate with the courage and the backbone to urge the Democratic Party to stop taking lobbyist contributions," said Jennifer O'Malley, Edwards' Iowa state director. "If Sen. Obama is serious about reform, he should join John Edwards in this challenge."

For her part, Clinton pushed through blinding snow to a sparsely attended church service in Waterloo, bringing her husband to introduce her to an African-American congregation in one of the state's largest minority communities. She later visited a veterans home.

All three Democrats will resume their campaigns in Iowa on Wednesday, eight days before the first votes of the 2008 election are cast in the state's caucuses.

Clinton is planning to restart her campaign with a new slogan, "Big Challenges, Real Solutions - Time to Pick a President," that she hopes will convince undecided voters that she is more experienced than Obama.

Obama is launching a "Stand for Change" tour in the final days, and aides said he will also focus on the question of electability.

Even with the caucuses on the immediate horizon, Clinton and Edwards will make at least one more stop in New Hampshire before Jan. 3, with an eye toward that state's first-in-the-nation primary on Jan. 8.

By Anne E. Kornblut and Perry Bacon Jr., The Washington Post, December 24, 2007