If GOP consultant Karl Rove is trying to figure out why he’s struggling to rally support for his causes, maybe he should remember an old truth: that the Republican Party’s true strength is its conservative base. Donations to Rove’s three political groups have dropped an astounding 98 percent since he waged his war on the tea party. Much of that decrease may be because 2013 was not an election year. But the plunge can also be attributed to donors’ realization that Republican candidates generally win elections only when they act Republican and not “Republican light.” In 2012, Rove-founded groups took...