GREENVILLE, South Carolina - Seeking an edge on the national security issue, Republican presidential hopefuls on Saturday seized on the attack in Texas this week for which Islamic State claimed responsibility as an example of the threat they say the militant group poses to the United States."It's not a matter of if another attempt is made on American soil, it is when," Wisconsin Governor Scott Walker said at a gathering of declared or potential contenders in South Carolina. "I want a leader who is willing to take the fight to them before they take the fight to us."Several potential contenders lambasted Obama for his refusal to describe the militants as adherents to a radical religious code and painted the conflict as one comparable to America's struggle against German Nazism and Soviet Communism."The great issue of our time is a battle between the Western values of freedom and this totalitarian worldview of Islamic fanatics," said former Texas Governor Rick Perry.