Voters in the U.S. state of New Hampshire are casting ballots Tuesday in the first primary election of the 2012 U.S. presidential campaign.

Residents in the small town of Dixville Notch, near the Canadian border, cast their votes in the Republican Party primary shortly after midnight local time . Officials there say former Massachusetts Governor Mitt Romney and Jon Huntsman, the former U.S. ambassador to China, each won two votes of the nine ballots cast. Voters in the rest of the state were due to go to the polls later in the day.

Romney held a large lead in public opinion polls ahead of Tuesday's primary, but that did not keep his main challengers from intensifying their attacks on him during last-minute campaigning Monday.

Much of the criticism has centered around Romney's previous career running a private investment firm where he made millions of dollars. Many people say Romney's firm laid off hundreds of employees from companies it bought, while making large profits for the investors.

Ex-U.S. Senator Rick Santorum, who lost to Romney by only eight votes last week in the Iowa caucuses, is hoping to also come in second in New Hampshire. But the latest polls suggest second place may go to Texas Congressman Ron Paul.

Besides Huntsman, the other major contenders for the Republican nomination include Texas Governor Rick Perry and ex-House Speaker Newt Gingrich.

All the candidates have been seeking to highlight their conservative credentials against the more liberal President Barack Obama, a Democrat.

Mr. Obama is facing no major challengers in Tuesday's primary vote. The president won three votes in Dixville Notch.

Many political analysts think next week's primary election in South Carolina will reveal whether the moderate Romney can rally the support of conservative voters.