Eyes in United States on Marco Rubio as Republicans take debate stage again today

US Senator Marco Rubio  speaks during a campaign rally in Pewaukee, Wisconsin,
US Senator Marco Rubio speaks during a campaign rally in Pewaukee, Wisconsin, PHOTO: BLOOMBERG

MILWAUKEE/WASHINGTON (REUTERS) - Republican presidential candidates will take the stage in Milwaukee in the second economic-themed debate in as many weeks, with voters and donors looking to see if US Senator Marco Rubio can produce another strong performance like the one he delivered two weeks ago.

Eight Republicans seeking the party's nomination for president in the November 2016 election will debate a range of economic issues. That is a smaller field than past debates after two candidates were bumped to the earlier, "undercard" forum.

Voters will watch how the candidates, including retired neurosurgeon Ben Carson and real estate magnate Donald Trump, handle detailed policy questions after criticism that their plans are too vague and overly political.

Rubio is under pressure to show he can fight off recent criticism of his experience, and his stance on abortion, as he tries to unseat fellow Floridian Jeb Bush as the favourite of the party's establishment.

Rubio has not led polls in any early-voting state, and lags Bush and others in fund-raising. A strong performance could change that.

"Right now, the establishment money guys are wondering, if not Bush, then who?" said Saul Anuzis, a former chair of the Michigan Republican Party who is backing U.S. Senator Ted Cruz of Texas. "Rubio has to show the leadership establishment types that he would be a good alternative to Bush."

The last debate gave Rubio a high-profile boost. Paul Singer, a hedge-fund billionaire who pumped millions into the 2012 elections, backed the 44-year-old late last month. Then a top Florida fundraiser defected from Bush's camp to Rubio's.

But Rubio has been dogged by criticism, much of it from the Bush camp, over missed Senate votes. Rubio's campaign recently released credit card records to fend off rumours he misused party funds while in Florida's legislature.

Bush supporters also believe Rubio's opposition to abortion even for victims of rape or incest is too extreme.

But it is unclear how much focus those issues will get on Tuesday. Fox Business Network aims to keep the candidates talking about the economy, after rival network CNBC was slammed for not sticking to policy in the last debate.

The economic theme plays to Rubio's strength. He has pitched his ideas to average Americans by talking about higher-education reform and a proposed tax credit for families.

Bush must translate a long list of carefully honed policy ideas to speak more eloquently about Americans' everyday problems.