Republicans know they’re going to have to budge on revenues in the looming debt and spending debate. The question is when to blink. The problem: Revenue increases, which could solve the fiscal cliff riddle this fall, are also their best bargaining chip for an even bigger fight to overhaul the Tax Code expected next year. GOP lawmakers — especially those on the tax-writing Ways and Means Committee — say tax increases should happen only as part of a fundamental Tax Code rewrite that also lowers marginal tax rates, a policy dream that won’t be realized until next year at the...