The last time it was the Republicans' turn to capture the governor's mansion, the year was 1994. Turn? Yes, every eight years since Pennsylvania's constitution has permitted governors to run for a second term, no incumbent has failed to win reelection, and no member of the incumbent's party has won a campaign for an open governor's office.

So all Republican eyes should be riveted to the primary race for governor, right? Not quite - thanks to the eclectic voting record of Sen. Arlen Specter.

Until February, conservatives across the state were searching for someone in the GOP mainstream to challenge Specter, and the only taker was pro-life activist Peg Luksic.

This was not unlike 1993, when the state's moderates, including Arlen Specter, were out recruiting candidates to run against a front-running conservative firebrand - me. They tried to lure one of the five more-moderate GOP contenders for governor into the Senate race. But the governor's mansion was too enticing.

Not this time. Six weeks ago, our U.S. Senate race changed for the most unlikely reason: Pennsylvania's master politician made a huge miscalculation. He did so by voting for President Obama's behemoth federal stimulus legislation.

What explains the miscalculation? Specter has been stewing for months on an even thornier issue: the elimination of the secret ballot in union elections, known as card check.

Last year, Specter was the lone Republican who voted to end the filibuster of the pro-union legislation. But even with all 51 Democrats, supporters fell short of the 60 votes they needed. Now, with 58 Democrats in the Senate and Al Franken still ahead in the Minnesota recount, Specter's vote would have been the decisive one.

Few issues unite Republicans more than card check. We all see it for what it is: taking away the working man's secret ballot in order to help one arm of the Democratic Party gain money and power. Team Specter had come under withering attack from conservatives since his card-check vote last fall. His own supporters warned of dire consequences should he be the vote to pass this game-changing partisan power play.

Message received; Specter announced this week that he would not support the legislation. But how could he limit the backlash from his pro-card-check supporters? Help them on other priority legislation - such as the stimulus package.

That's not to say Specter did not honestly support the stimulus bill. He did. He's a member of the Senate Appropriations Committee who votes for government spending because he believes it has helped solve many problems confronting this country.

Although other Republicans warned Specter that the stimulus package was no ordinary appropriations bill, he saw it as a chance to put the spotlight on a position that seemed right to him on both policy and politics.

A mistake? Ask Pat Toomey. Until that vote, the former Lehigh Valley congressman was telling everyone he was not going to reprise his primary challenge to Specter five years ago. But after The Vote, Toomey changed his tune; now he's singing his greatest hits of 2004.

The playing field looks promising for Toomey. Polls have Specter's reelect number among Republicans at 25 percent - stunningly low.

That's not the worst of it. Specter beat Toomey by 17,000 votes in 2004 largely by winning Southeastern Pennsylvania by 42,000. But since then, more than 83,000 Specter-supporting Republicans in the region have left the party.

Pennsylvania's political Houdini has escaped similar predicaments in the past by burnishing his conservative credentials in the run-up to the primary - hence the announcement on card check this week. So, too, his potentially crucial vote against Solicitor General Ellen Kagan, which conservatives are touting as a death knell for her chances of being named to the Supreme Court.

Specter is also fighting President Obama's bid for more government-run health care. The senator's conference room still features his famous Rube Goldberg chart, which contributed to the collapse of Clinton-care in 1994.

The argument that Specter has the best chances in a general election will become more persuasive next year, when the GOP faithful face the harsh reality that they are more than a million registered voters behind the Democrats. However, thanks to the prospect of facing Specter, whoever wins the primary will not face an A-list Democratic opponent.

In 2004, President Bush and a Senate colleague from Western Pennsylvania made the difference for Specter. Those dogs don't hunt anymore. This year, his help may come from Peg Luksic, Larry Murphy, and anyone else who helps split up the vote next spring - anyone other than Pat Toomey, that is.

It will be fun to watch. And watch I will.

E-mail Rick Santorum at rsantorum@phillynews.com.