Mitt Romney has finally found a groove on the right. But he could find himself stuck there if he wins the GOP nomination. With Romney’s recent move to wield the immigration issue as a club against Rick Perry — painting him as “soft” on a topic that resonates with the Republican primary electorate — the former Massachusetts governor is taking advantage of a rare opportunity to outflank Perry on the right among conservatives. After the Texas governor wounded himself with his remarks in the last debate, Romney seized on the issue of illegal immigration, trying to paint Perry as an...