Democrat Barack Obama worked to fend off an intensified attack on his foreign policy credentials from rival Hillary Rodham Clinton on Sunday as their paths crossed two days ahead of a potentially race-ending showdown in Ohio and Texas. "What precise foreign-policy experience is she claiming that makes her qualified to answer that telephone call at 3 a.m. in the morning?" Obama asked of the former first lady at a town-hall meeting. It was a reference to dueling television ads over who would exercise superior judgment in responding to a national emergency in the middle of the night. The Illinois senator also sought to ease lingering Internet-fed concerns about his religion, in particular whether he was a closet Muslim. "I am a devout Christian. I have been a member of the same church for 20 years. I pray to Jesus every night," he declared at an earlier appearance in the rural southern Ohio town of Nelsonville. He said he wanted to halt "confusion that has been deliberately perpetrated."