Romney faces tough battle ahead of Super Tuesday

The two leading Republican primary candidates are each hoping to take come out well ahead on next week's Super Tuesday, when 10 states vote at once and one-fifth of the crucial convention delegates are up for grabs.

In the battle to decide which Republican candidate will take on Democratic President Barack Obama in November's general election, Romney has now won six states and Santorum has won four, with former House speaker Newt Gingrich trailing on one.

Delegates are awarded by each state in the complex Republican party nominating process, sometimes on a proportional and/or non-binding basis, until one candidate reaches the 1,144 delegate threshold required for victory.

If the race continues to be tight it is possible that no winner will emerge before the Republican convention at the end of August, in which case a victor may have to be decided by backroom brokering.

Mitt Romney is once again the clear favorite for the Republican presidential nomination after romping to victory in Arizona and surviving a high-stakes primary test in his native Michigan.

But while he billed his double win as a "decisive" turning point in the volatile race, his opponents are still scenting blood as they know he almost came unstuck in two strongholds that really should have been cakewalks.

Rival Rick Santorum failed to pull off the upset he hoped for in Michigan but vowed to come back hard on Super Tuesday.

"We'll show that we are the alternative if you want a conservative," the devout Catholic and fierce opponent of gay marriage and abortion told Fox News. "We're going to compete and do exceptionally well on Super Tuesday."

Grandees in the Republican establishment hoping that Romney's latest wins will give him unstoppable momentum and avoid a long and bitter fight may be disappointed, experts say.

"It's kind of a mixed and scattered picture," Charles Franklin, a politics professor at Marquette University Law School, told AFP, highlighting the importance of next week's vote in Ohio, a key general election battleground.

"Most Super Tuesdays, the winner doesn't win absolutely everything but they're able to brush aside their losses by being able to point to important wins," said Franklin, also the co-founder of pollster.com.

"I think Ohio does loom large because it's the biggest, it's the most competitive, it has implications for the fall. There is a lot of psychology and spin here, but it's very hard to spin away a loss in Ohio."

Santorum, who was senator of neighboring Pennsylvania and has proudly touted his coal miner grandfather, was already campaigning on Tuesday in the Rust Belt state and has opened up a lead there in recent polls.

He says his strong performance in Michigan proves that Romney, a multimillionaire businessman and former governor of liberal Massachusetts, is out of touch and highly vulnerable in Ohio, which has a similar make-up.

It was estimated Santorum and Romney would both receive half of Michigan's 30 delegates, but it was the headline loss for Santorum in the popular vote -- albeit by a slim 41 percent to 38 percent margin -- that was all-important.

"If Santorum could have spent the next week talking about his big win in Romney's home state that would have been far more powerful," Franklin said.

Despite yet more wealth-related gaffes, Romney put in a strong debate performance when it mattered and used his financial muscle to successfully portray Santorum as a Washington insider.

"I think there's a pattern here," said Franklin.

"It seems to me that when Romney gets in trouble, he's been able to mount aggressive advertising campaigns and often debate performances which really have brought him back to wins.

"These alternatives to Romney generate some short-term surges of support but in the face of the withering criticism from the Romney campaign they have been so far unable to sustain their strength."

All this negative Republican infighting is gift-wrapped fodder for Obama, who tore into his opponents for attacking his successful bailout of the Michigan-based auto industry.

The White House has no problem with a long primary battle that allows the president to keep pushing his jobs message in key November battlegrounds while his potential rivals slug it out.

All four remaining candidates -- including Gingrich and congressman Ron Paul of Texas -- have vowed to stay in the race until the convention.

The only vote before Super Tuesday is a non-binding caucus in Washington state on Saturday.