Wisconsin Congressman Paul Ryan is a top contender to be Mitt Romney’s running mate, and that’s launched a heated debate in GOP circles. As House Budget Committee chairman, Ryan was the driving force behind the GOP’s controversial tax plan, and some say he could add some much needed policy heft to Romney’s rather general campaign. Others, however, argue that if Romney picks Ryan he will be inviting an unfavorable showdown over Medicare, since Ryan’s budget proposal would have revamped the program as a voucher-based system. The speculation over Ryan symbolizes a larger debate going on in GOP circles: whether Romney’s campaign should continue its cautious strategy of simply criticizing Obama until Election Day or adopt a more assertively conservative stance.