Newt Gingrich is outpacing Mitt Romney by a comfortable margin among Republican voters nationwide, but also is showing evidence of the vulnerabilities that could hurt the former House speaker in a general election, according to the latest Wall Street Journal/NBC News poll. With the two rivals fighting it out in Florida after Mr. Gingrich's big South Carolina victory last week, the poll found Republicans nationwide favoring Mr. Gingrich 37% to 28% over Mr. Romney. GOP voters gave the former House speaker high marks for knowledge and experience, while they continued to harbor doubts about Mr. Romney's positions on the issues...