Likely Opponent In Primary Looks to Tap Anger on Right. BY PERRY BACON JR. PHILADELPHIA, April 13 -- Sen. Arlen Specter's support for President Obama's stimulus package has recharged a political rivalry, setting up what could be a divisive rematch between one of the GOP's leading moderates and a powerful conservative activist. Pat Toomey, head of the anti-tax Club for Growth, stepped down from the post Monday, the first move in what his aides say is an almost-certain run against Specter in next year's Republican Senate primary. In the 2004 primary, Specter defeated Toomey by 17,000 votes out of more...