From NBC/NJ's Aswini Anburajan
Des Moines, IA -- Senator Barack Obama pointed to the chilly weather in Iowa Saturday, to show that his campaign is entering into a new season on the campaign trail, in which he will draw stronger distinctions between himself and his rivals in the Democratic primary.
 
"Now as the leaves turn and the air gets cooler, we'll have more emphasis on the contrast between myself and the other candidates in the race," Obama said during a door-to-door canvass in Des Moines.

Obama, responding to the recent back and forth between his campaign's and Hillary Clinton's on the issue of Iran, said that these are the types of distinctions voters want to hear about and did not mark a departure from his pledge to run a positive campaign.

"None of these difference rise I think to the level of personal attacks or gratuitous attacks.  And that's the kind of politics I think people are tired of, but they certainly want to hear from the candidates where do you differ in terms of Iraq, where do you differ in terms of Iran, how would you actually deliver on healthcare as opposed to just talk about it," Obama said.

He added that the sharpest contrasts between himself and Clinton was in the area of foreign policy, and he pointed to Clinton's vote on Iran as a sign that her positions do not stray too far from the current administration.  

"I think on foreign policy she tends to think more conventionally at a time when we are facing a series of unconventional quests," Obama said.  "She may be willing to go along with Bush policies that provide rationale for keeping troops longer in Iraq or engaging in force towards Iran."

On domestic differences, Obama said that he and Senator Clinton overlap on many issues, including health care, but that the real difference between them was who could most effectively carry out their agenda, alluding to the idea that Clinton could polarize the electorate.

"But the real question is who can bring the country together and overcome the special interest driven agenda in Washington to deliver on a plan for universal healthcare, or to deliver on a bold energy police. And I would not be running if I didn't think I was going to be more effective in breaking out of the gridlock in Washington," he said.

The campaign's push to draw bolder distinctions between Obama and Clinton reflect the widening lead Clinton has had in national polls, and also in Iowa, where last week's Des Moines Register poll had her six points ahead of Obama.

But Obama spun his low poll numbers into a question of name recognition among Democratic voters, rather than an indication that his message is not taking hold.

"We always knew that I've got to introduce myself to voters in the way that some of the other candidates don't have to do," Obama said. He added that the campaign would rely on grassroots organizing and one on one interaction with Iowans in town halls and events like Saturday's canvass, to get a leg up on his competitors.

Giving a nod to the role that Iowa played in his campaign strategy, Obama said, "I think it's crucial that we do well here."