With only one day of campaigning left before the first event of the U.S. presidential election process, Republican candidates are making last-minute pitches in the central state of Iowa.

On Tuesday, Iowa Republicans will hold party caucuses – meetings at which they will vote for their favorite candidates.

The latest voter surveys indicate that former Massachusetts governor Mitt Romney has the lead in Iowa among seven Republican contenders trying to unseat President Barack Obama, a Democrat.

Romney is closely followed by Texas Congressman Ron Paul. Former Pennsylvania senator Rick Santorum is in third place.

After days of criticizing each other, the Republican candidates focused on President Obama Monday.

Romney hammered away at Mr. Obama's record on the economy.

“He said if 'I can't get this economy turned around in 3 years, I'm looking at a one-term proposition.' I'm here to collect.”

Santorum attacked the Obama administration for regulations on business.

“People are saying, well what's hurting this economy? This president, and his top down, I know best, I'm going to tell you how to run your business, how to run your farm, how to run your life. The huge cost that that's putting on the American people and business is crushing this economy.”

Former congressman Newt Gingrich, who is well behind the leaders in the poll, also took aim at Mr. Obama, blaming him for the political divisions in Washington.

“What America needs is a president who thinks about the children and the grandchildren of this country and the future of this country, and puts that above his own petty, arrogant ambitions and instead serves the country.”

Voters in Iowa often do not crown the eventual presidential nominees for either Republicans or Democrats. But its first-in-the-nation caucuses can serve as a launchpad for political success in other states during the next several weeks of the candidate selection process. The Iowa caucuses also serve to push weaker contenders out of the race.

The final hours of the campaign may be crucial as a poll by Iowa's largest newspaper, the Des Moines Register, indicates 41 percent of voters have yet to make up their minds.

A seventh Republican candidate, Jon Huntsman, the former U.S. ambassador to China, has not campaigned in Iowa, instead pinning his hopes on a good showing in the northeastern state of New Hampshire, where voters will cast primary election ballots on January 10.

Mr. Obama is unopposed for his party's renomination, but he faces a difficult test to win another term. The nation's economy, the world's largest, has recovered sluggishly from the 2007-2009 recession, leaving many voters questioning his leadership.