In the days leading up to a critical Senate vote this month on the GOP tax plan, Republican Sen. Rob Portman, Ohio, met secretly with Sen. Joe Manchin III, W.Va., in the moderate Democrat's hideaway office in the basement of the Capitol.
Manchin told Portman that he would consider joining the tax effort, if only for a few changes. Chief among them: Instead of cutting the corporate tax rate to 20 percent, a top Republican goal, reduce it to 25 percent - and use the proceeds for bigger middle-class tax cuts. Other Democrats, Manchin suggested, might follow.
Portman took the request to Republican leaders, who rejected it.
For Republican leaders, the prospect of a bipartisan...