DES MOINES, Iowa (By Jeff Zeleny, NYTimes) December 2, 2007 As the countdown to the Iowa caucuses hits the one-month point, an already long and intense campaign enters a new level of engagement as candidates on both sides of the ticket battle ferociously for undecided voters.

The first three weeks of December, strategists say, may present an opportunity for candidates to give closing arguments.

Polls suggest that nearly half of likely voters are still willing to change their minds, and that has created an even more unsettled contest for Republicans and Democrats alike.

The Iowa caucuses are Jan. 3, but campaign officials hope to lock down their supporters by Christmas, fearing it will be difficult to break through in the week leading up to the new year.

Campaigns are making contingency plans to deal with winter storms, one of which all but brought the campaign to a standstill over the weekend. Telephone lists are at the ready, for candidates to call prospective voters one-by-one.

So with no clear front-runner in either party — at least in the opening contest, in Iowa — the campaigns are dispatching all available operatives, volunteers and surrogates to the state.

Campaign headquarters in Illinois, Massachusetts, Virginia and other states are preparing to clear out, with fund-raisers and other workers suddenly being told to go knocking on doors and encouraging Iowans to vote.

The clock is ticking, with 31 days before the opening round.