Hafer's announcement comes as speculation rises that the state's current treasurer, Robert Casey Jr., will soon announce his candidacy for the Senate in 2006.
Casey has been heavily courted by Washington Democrats, who see him as the party's best chance to defeat incumbent Rick Santorum, the Senate's No. 3 Republican. But the lobbying of Casey, who opposes abortion-rights, has upset organizations like EMILY's List, which backs pro-abortion-rights Democrats in primaries.
List spokesman Ramona Oliver said she's troubled by the party's efforts to clear the primary field. Her group, which LifeNews.com reported Thursday funneled $34 million to pro-abortion rights candidates in 2004, has already sent two staffers to Pennsylvania to help Hafer organize her campaign.
Casey said through a spokesman Wednesday he is very close to making a decision about whether to run. He told party leaders in February he would make the race only if he received assurances he would win the nomination.