Six weeks ago, Democratic insiders in the Keystone State were spinning the idea that Gov. Ed Rendell (D) wanted recently retired state Treasurer Barbara Hafer to be his party’s nominee against Sen. Rick Santorum (R-Pa.) next year. [IMGCAP(1)]

But now that newly elected state Treasurer Robert Casey Jr. seems to be re-considering his political plans (which initially centered on biding his time to run for governor in 2010) and may well be interested in a 2006 Senate bid, Rendell’s role in recruiting a Senate candidate for his party has gone from clear to cloudy.

Ultimately, however, Rendell can’t avoid being a key player, whether he throws his weight behind one hopeful or opts to maintain strict neutrality. He’s the 800-pound gorilla in the room that simply cannot be ignored.

While various party strategists have strong opinions about whether Casey or Hafer would be the stronger opponent for Santorum, a case can be made for each. One thing is sure: There is at least a trace of irony in the fact that both are mentioned as potential contenders for the Senate and suitors for Rendell’s attention.

Hafer was the Republican nominee against Casey’s father, then-Gov. Robert Casey (D), in 1990. In that contest, she drew just 32 percent of the vote — the worst beating a major party candidate suffered in Pennsylvania for either governor or Senator since World War II.

In addition, Hafer, who served two terms as state auditor and another two as state treasurer (all as a Republican), endorsed Rendell in his 2002 gubernatorial bid, eventually switching parties in late 2003.

Casey, whose father served two terms as governor but is now most remembered for being denied a speaking slot at the 1992 Democratic National Convention because of his opposition to legal abortion, lost to Rendell in the 2002 primary for governor. State Treasurer Casey’s brother, Pat, lost a bid for Congress to Don Sherwood (R) in 2000.

Supporters of Casey note his family’s name identification and exemplary reputation, combined with his appeal among “Reagan Democrats” and proven votegetting ability statewide — but particularly in northeastern and western Pennsylvania — would make him a formidable opponent for Santorum.

Liberals and supporters of Hafer counter that Casey’s views on abortion would cost him crucial support in the vote-rich southeastern corner of the state, particularly among women and supporters of legal abortion (including moderate Republicans in Philadelphia’s Main Line suburbs), who backed Rendell, Al Gore and John Kerry.

Hafer supporters invariably try to raise doubts about Casey by comparing him to Santorum’s 2000 opponent, then-Rep. Ron Klink, a Pittsburgh-area Congressman who also opposed abortion rights and gun control and who was hammered in the general election by Santorum.

Casey’s supporters counter, quite correctly, that their candidate has proven statewide votegetting ability and immediate credibility, both of which Klink lacked. In fact, Casey’s ability to neutralize social issues, while keeping Santorum on the defensive over jobs, health care, Social Security and other domestic issues has Republican strategists privately very worried about the race.

Last year, Casey drew more than 3.3 million votes for state treasurer, more than any candidate, for any office, in state history. And he carried Westmoreland County (in the western part of the state) by 45,000 votes at the same time that Bush was winning it by 22,000 votes.

Keystone State Democrats and the Democratic Senatorial Campaign Committee (to say nothing of Casey and Hafer) would prefer to avoid a primary; that’s where Rendell comes in.

If Hafer jumps in early and is endorsed by the governor, it is less likely that Casey would also make a Senate run. She would almost certainly attract considerable pro-choice money (that would not be available to Casey under any circumstances), raising the specter of a difficult primary for the state treasurer.

On the other hand, if Casey runs for the Senate, pro-choice Democrats, particularly in and around Philadelphia, might well promote a candidate against him.

It is difficult imagining EMILY’s List, for example, sitting back and allowing the pro-life Casey to become the Democratic nominee. Former Congressman Joe Hoeffel, the unsuccessful Democratic nominee against Sen. Arlen Specter (R) last year, would be an obvious possibility, but a number of potential female candidates would also be considered.

But Rendell is so popular with Philadelphia-area Democrats that even if he couldn’t prevent a primary challenge to Casey, he could erode anti-Casey primary opposition by throwing the full force of his political muscle behind Casey, virtually guaranteeing his nomination for the Senate.

Hafer’s appeal duplicates (or, if you prefer, replicates) Rendell’s, while Casey’s strength outside Philadelphia and more conservative reputation on guns and abortion compliments the governor’s.

It makes sense for Rendell to do whatever he can to woo Casey into the Senate race, while promising Hafer support in 2010, when his second term would end. That figures to be a GOP year in Pennsylvania anyway, given the state’s eight-year partisan cycles, another reason Casey might prefer the 2006 Senate race.

Normally, politicians up for re-election prefer to remain neutral in other statewide contests, and Rendell might prefer to keep his hands clean in the maneuverings for the Senate race. But he could clear up the Senate haze quickly if he took the lead.

Stuart Rothenberg is editor of the Rothenberg Political Report.