Former state Treasurer Barbara Hafer yesterday signaled her plans to seek the Democratic nomination for U.S. Senate, and a spokesman for her successor, Bob Casey Jr., said his decision on whether to enter the 2006 contest was imminent.

Should both candidates decide to press on, that would set up a scenario that national and state Democratic leaders had hoped to avoid -- an expensive, potentially debilitating primary battle as a prelude to the Democrats' challenge of one of their prime 2006 targets, Sen. Rick Santorum.

"We are very close to a decision," Karen Walsh, a spokeswoman for Casey, said yesterday. "It will definitely come this week."

While Casey and Hafer have talked privately about avoiding a primary fight, Hafer didn't wait for Casey's public announcement.

"We're in it," she said in an interview with The Associated Press. "I'm getting a campaign up and running."

The Web site PoliticsPa reported yesterday that Casey also had decided to enter the race. Walsh insisted, however, that Casey had not made a final decision.

"There are some things we still need to address," she said.

Hafer may be chief among them. The day's maneuvering conjured political deja vu on a number of levels. Hafer, while still a Republican, waged an unsuccessful statewide race against Casey's father in his 1990 re-election as governor. She planned another run for governor in 1992, again as a Republican, but the party hierarchy turned instead to then-Attorney General Mike Fisher.

Hafer, a former Allegheny County commissioenr, got her revenge by endorsing Fisher's eventual opponent, Gov. Ed Rendell, and later switched to the Democratic Party. She had acknowledged her interest in a possible challenge to Santorum, while senior Democrats, including Rendell, had referred to her as a promising potential challenger.

But after Casey Jr. amassed a record vote total in succeeding her as treasurer, national Democrats approached him about taking on Santorum.

Many Democratic party leaders view Casey as an attractive challenger because he is a conservative on social issues including abortion and gun control, giving him the potential to offset Santorum's appeal to more conservative Democrats.

"I told him he would be a great candidate and if it's what he wanted to do, he should go ahead and do it," Rendell told reporters in Harrisburg yesterday. "I think Bob Casey is a bright, capable person who would do a good job in anything. ... It's not going to be an easy election, but if anybody can give Sen. Santorum a fight, it's Bob Casey."

Among the senior Democrats who have courted Casey are Sen. Harry Reid of Nevada, Democratic leader of the Senate, and Sen. Charles Schumer, D-N.Y., chair of the Democratic Senatorial Campaign Committee. Casey had promised them an answer by this week.

A survey of Pennsylvania voters last month by Quinnipiac University showed Casey with a lead of 46 percent to 41 percent over Santorum. The poll of 1,250 voters, with a margin of error of plus or minus 2.8 percent, depicted the incumbent leading other potential Democratic opponents, including Hafer.

Answering the Quinnipiac finding that she trailed 47 percent to 39 percent in a Santorum matchup, Hafer subsequently released a survey she had commissioned which, she said, showed her in a virtual tie with him.

Hafer, who has longed favored abortion rights, said further that her poll showed that a majority of Pennsylvania voters, and 60 percent of Democratic voters, agree with her on that highly charged issue.