Most Washington, D.C., insiders know former Rep. Pat Toomey, R-Pa., as a stalwart conservative.

As the former president of the anti-tax Club for Growth, Toomey often made it his mission to defeat Republican members who did not meet his group’s conservative standards on spending.

But ever since Sen. Arlen Specter of Pennsylvania made the switch to run for re-election as a Democrat, Toomey has been forced to recast himself as more of a centrist as he prepares for the 2010 general election...