Of the handful of candidates left in the rollercoaster Republican presidential race, Rick Santorum seems to stir more emotions than most with his radical views on religion, women and marriage.

Despite his staid knitted sweater vest and easy boyish smile, Santorum is given to passionate outbursts when he talks about God and country which have endeared him to right-wing conservatives.

But those same strong conservative views, born from his Catholic faith, are giving many pause as Republicans struggle to coalesce around one candidate to take on Democrat President Barack Obama in the November elections.

The 53-year-old former Pennsylvania senator was a virtual unknown when he first threw his hat into the ring in June last year to be the Republican Party's nominee.

Despite being written off early on, Santorum has built his campaign state-by-state -- a David and Goliath struggle against a Mitt Romney juggernaut powered by a huge war chest and a solid organizational machine.

On Super Tuesday, Santorum added three more states to his string of four earlier wins, taking Tennessee, Oklahoma and North Dakota.

He also battled Romney to a knife-edge finish in Ohio, just losing out in the key bellwether state.

Fired up, Santorum promised he was fighting on.

"Tonight it's clear: we've won races all over this country against the odds. When they thought, 'oh OK, he's finally finished,' we keep coming back," Santorum told a packed gymnasium at Steubenville High School, Ohio.

His pro-life, anti-contraception, marriage-only-between-a-man-a-woman message has gained traction with heartland evangelicals deeply skeptical of Romney, who they view as a moderate disguised in conservative clothing.

Yet on the other end of the spectrum, critics see his radical right-wing views as somewhat scary. A website called "Santorum exposed" says it is dedicated to "shining a bright light" on what it calls the former senator's "extreme positions."

Santorum is a global warming skeptic, has called Obama "a snob" because he believes all kids should have a college education, and said he wanted "to throw-up" when watching former president John F. Kennedy talk about the separation of church and state.

"I don't believe in an America where the separation of church and state is absolute," he told ABC on Sunday.

At a campaign stop in Ohio last month, Santorum also hit out at Obama saying the president's "world view" elevated the Earth above man.

"That's what I was talking about -- energy: this idea that man is here to serve the Earth, as opposed to husband its resources and be good stewards of the Earth. And I think that is a phony ideal."

Asked to define himself in one word at a recent debate, Santorum replied "courage." That steely resolve, refusing to stray off his message of "Family, Faith and Freedom," has defined his campaign even as it struggled.

A father of seven and trained lawyer who has been married to his wife Karen for 21 years, Santorum was first elected to the House of Representatives for Pennsylvania in 1990. He served two terms in the US Senate from 1995 to 2007.

In an intensely personal speech following his early win in Iowa, Santorum described his roots in Pennsylvania's coal country, where his grandfather fled in 1925 and worked in the mines until he died at 72.

"I knelt next to his coffin. And all I could do -- eye level -- was look at his hands. They were enormous hands. And all I could think was those hands dug freedom for me."

Santorum has often spoken of his seriously ill youngest daughter, Isabella Maria, who suffers from a genetic disorder, trisomy 18 -- or Edwards syndrome -- which results in severe disabilities and abnormalities.

He had to break away from the campaign trial in January to be by her bedside as the three-year-old recovered from treatment.

He has also tearfully recounted a family tragedy in 1996 when a son died hours after being born prematurely. He and his wife spent the night with the body and brought it home to show to their other children before burying it.

"Ask me what motivates me, it's been the dignity of every human life," Santorum said in his Iowa speech.

Despite his latest wins in the Super Tuesday bonanza though, doubts remain whether Santorum has the organizational ability and political chops to defeat Romney in the long nominating process to secure the Republican Party crown.