Republican presidential contender Herman Cain is facing attacks on his tax reform plan from nearly all of his competitors at the party's latest debate at a Las Vegas casino.

The heated discussion Tuesday evening in Nevada highlights Cain's recent rise as one of the leading candidates in the race for the Republican presidential nomination.

Cain, a former pizza company executive, has never held office, but is popular among conservatives. Some recent polls show him holding first place, in front of former Massachusetts governor Mitt Romney who has long been a favorite to win the nomination.

Cain has gained attention for his “9-9-9” plan that eliminates current federal taxes and replaces them with nine percent corporate, income, and sales taxes. Some analysts say his plan will greatly increase the amount of taxes lower-income Americans will have to pay.

Other topics on the agenda include the economy, illegal immigration and border security.

Also participating in Tuesday night's debate are Texas Governor Rick Perry, Minnesota Representative Michele Bachmann, Texas Representative Ron Paul, former Pennsylvania senator Rick Santorum and former House speaker Newt Gingrich.

Former Utah governor Jon Huntsman is not participating in the debate in protest of Nevada's decision to move up the date of its caucus to January 14.

Meanwhile Tuesday, the Iowa Republican Party has set January 3, 2012, as the date for the first state contest to select a party presidential candidate.

The Iowa caucus is seen as the crucial first step in narrowing down the field of candidates.