Back in November, Sen. Orrin G. Hatch, the 83-year-old Republican from Utah, was at the helm when the Senate's massive tax bill came through the Finance Committee. But Hatch also deputized four younger Republicans on the panel to serve as de facto co-chairmen over various parts of the legislation. This week, with a compromise bill marching toward final passage in both chambers, the House will take the unusual step of voting first - because a pair of senators, Thad Cochran, R-Miss., and John McCain, R-Ariz., are recuperating from, respectively, non-melanoma skin surgery and the side effects of cancer treatments. Hatch's...