Republican Scott Brown portrayed himself as independent of the national party. But his successful bid for a U.S. Senate seat received big support from the GOP leadership in Washington and from the political machinery of former Massachusetts Gov. Mitt Romney. For Republicans, the Massachusetts win points to a strategy that could help the party bridge the split between grass-roots activists and the national establishment. Mr. Brown effectively ran against Washington and repeatedly vowed to be an "independent" thinker if sent to Capitol Hill. The message appealed to disenchanted voters, especially independents. At the same time, without fanfare, the Republican National...