Thornburgh Quits Post to Make Bid for Senate : Politics: The attorney general will run for the unexpired term of the late Sen. John Heinz of Pennsylvania.

Atty. Gen. Dick Thornburgh resigned Friday to run for the unexpired term of the late Sen. John Heinz (R-Pa.), a move he has planned for more than two months.

Administration sources said White House Chief of Staff John H. Sununu is pushing hard for Missouri Gov. John Ashcroft as Thornburgh’s replacement, but Bush is not expected to nominate a candidate until after he returns to Washington Sept. 3.

The Senate would not be able to begin the confirmation process until at least Sept. 10, when lawmakers return from their August recess. Bush has said Deputy Atty. Gen. William P. Barr will serve as acting attorney general after Thornburgh’s resignation becomes effective Thursday.

Barr, 41, is also on the list of possible candidates to replace Thornburgh, but sources said some White House officials believe he is too young and his appointment would not bring Bush any particular political advantage.

Sununu is said to favor Ashcroft because the 49-year-old governor is staunchly anti-abortion and a solid supporter of the conservative social-policy agenda. Administration officials have named a number of others as potential candidates, including White House Counsel C. Boyden Gray.

Thornburgh announced his intention to resign and run for the Pennsylvania Senate seat in early June, but he said he wanted to stay through part of the summer to work on the President’s crime and civil-rights bills. The crime bill enjoyed some success in Congress, but that was overshadowed by controversy over whether the Justice Department failed aggressively to pursue reports of criminal activity at the Bank of Credit and Commerce International.

On the defensive, the Justice Department said a task force of 10 federal prosecutors in three cities is studying the bank’s activities.

Thornburgh was also hit with criticism that the department acted irresponsibly by siding in court with anti-abortion demonstrators who staged a protest in Wichita, Kan., that has resulted in about 2,000 arrests.