Hours before the Iowa presidential caucuses, some Republican presidential candidates appealed to young voters for their support.

At a high school outside the state capital, Des Moines, Texas Congressman Ron Paul promoted his anti-war stance.

“There is no reason in the world that we cannot be strict constitutionalists, strong national defense and say that we should not send young people off to war unless it's absolutely necessary and necessary for our national security.”

At that same “Rock the Caucus” event, former Pennsylvania senator Rick Santorum encouraged students to hold their president and presidential candidates accountable.

“Every decision that's going to be made during the next few years, whether 'Obamacare' is repealed or whether it's kept in place, whether taxes are going to grow, whether this deficit that is now crushing the economy and will crush your pocketbooks in the future is going to be dealt with so you won't have a lower standard of living. Those are the issues.”

Minnesota Congresswoman Michele Bachmann also touched on the taxes issue, highlighting her experience as a tax lawyer.

“I want to abolish the tax code and do away with it and put in its place a pro-growth code, so that you can widely succeed with your future and with your plans.”

Later Tuesday, residents will brave the winter cold to cast their votes at party caucus meetings — the first event in the process of electing a new U.S. president later this year.

The latest polls show former Massachusetts governor Mitt Romney leading the Republican contenders.

Small-government advocate Paul is close behind and social conservative Santorum is in third. But with nearly half of Iowa voters saying they are still making up their minds, the outcome is impossible to predict.

Romney on Tuesday criticized President Barack Obama's record on Iran, the economy and job creation.

“This has been a failed presidency. I will go to work to get Americans back to work and make sure that job one is concentrating on jobs for Americans, not just keeping one's own job.”

Voters in Iowa often do not crown the eventual presidential nominees for either the Republicans or Democrats. But the state's caucuses can push weak contenders out of the race, or propel stronger candidates to success in other states during the next several weeks.

Of the seven Republican contenders, one, the former U.S. ambassador to China Jon Huntsman, has not campaigned in Iowa. He is pinning his hopes on a good showing in the New Hampshire state primary January 10.

The Democratic party also holds its caucuses Tuesday. President Obama is unopposed for the Democratic nomination, but he faces a difficult test to win another term in the November election. The nation's economy has recovered sluggishly from the 2007-2009 recession, leaving many voters questioning his leadership.

Mr. Obama returned to Washington Tuesday after a 10-day vacation in Hawaii and will host a live web chat with supporters in Iowa Tuesday night as the caucuses take place.