Donald Trump's lead in public opinion polling could have a soft underbelly, leaving him more vulnerable than the numbers might suggest. The New York real estate mogul and reality television star paces the field of Republican presidential candidates nationally, garnering an average of 35.1 in the Huffington Post polling tracker. Rounding out the top four candidates are retired pediatric neurosurgeon Ben Carson, with 13.9 percent and Sens. Marco Rubio of Florida and Ted Cruz of Texas, with 12.6 percent and 11.4 percent, respectively. But use the site's custom filter to remove surveys conducted via the Internet, Interactive Voice Response, a...