by Anthony Salvanto, Jennifer De Pinto, Sarah Dutton, Fred Backus

With less than two months before the official kick-off of the 2016 presidential election, Hillary Clinton has an edge in Iowa, the nation's first contest, and a big lead in South Carolina, where she is ahead of Sanders by two-to-one, while Bernie Sanders still leads in New Hampshire. Former Maryland Gov. Martin O'Malley is a distant third in all three states.

Clinton and Sanders supporters in Iowa are equally as enthusiastic about their candidate, but Sanders has the enthusiasm advantage in New Hampshire. Seventy-six percent of his voters say they are enthusiastic in their support for him, compared to 49 percent of Clinton backers who say that about her.

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After months of campaigning and three debates, Democrats seem generally okay with the tone and tenor of the campaign, and mostly good feelings between the supporters of the candidates. Seventy-nine percent of Sanders' supporters in Iowa and 75 percent in New Hampshire say Sanders has put forward about the right amount - not too much, not too little - of criticism toward Clinton, and only a 25 percent of his New Hampshire backers would like him to be tougher. Slightly fewer - 17 percent - say this in Iowa.

And Sanders' backers are okay with Clinton's message, too: more than seven in ten Sanders backers in both states say they like what Clinton is saying, generally, too, but they just like Sanders better as a candidate. Only one in five Sanders backers in Iowa and New Hampshire says they don't like the things Clinton is saying. Clinton backers are generally positive toward Sanders.

Few Clinton voters think she should be more critical of him.

Democratic primary voters were asked what information sources have impacted their vote choice recently. In Iowa, how the candidates have handled interviews and speeches tops the list (72 percent), ahead of candidates' reactions to news events (48 percent), debate performances (41 percent) and meeting the candidates in person (26 percent). Views among Clinton and Sanders supporters are similar.

In the aftermath of the Paris and San Bernardino attacks, about half of Democratic voters in the early states say America is becoming a more insecure and dangerous place. Among Republican voters that number rises to nine in 10.

Iowa, New Hampshire and South Carolina Democrats oppose a temporary ban on Muslims entering the U.S, while majorities of Republican voters in these states support such a ban.

Methodology and complete results can be found below and here. The CBS News 2016 Battleground Tracker is a panel study based on interviews conducted on the internet of registered voters in Iowa, New Hampshire, and South Carolina between December 13-17, 2015 with a total of 3,812 interviews. The poll was conducted by YouGov, an online polling organization.