LAHORE, Pakistan  The only Christian cabinet minister in the Pakistani government was shot dead Wednesday two months after the assassination of another liberal politician, raising questions about how firmly Pakistan’s government is tackling Islamist extremism.

The slain official, Shahbaz Bhatti, 41, the minister of minorities, had made a life’s work of campaigning for tolerance in Pakistan, which is 95 percent Muslim, and most recently became a lonely voice, with a handful of others, in a campaign to reform the harsh blasphemy law.

After the assassination in January of the Punjab Province governor, Salman Taseer, who had also publicly called for changes to the blasphemy law, Mr. Bhatti feared for his life but continued, though more quietly, to work toward his dream of ultimately repealing the law, his associates said.

The law, introduced in the 1970s, was amended in 1986 under Gen. Mohammad Zia ul-Haq, the American-backed military leader, to include the death penalty for those accused of speaking against the Prophet Muhammad.