David Drucker of the Washington Examiner takes a closer look at Donald Trump’s presidential polling numbers.

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 combination of IVR and online and through automated telephone interviews, and the data looks significantly different. Using only polls conducted via interviews with live telephone operators, Trump’s still commanding position in the national GOP average drops to 27.2 percent; Carson’s number rises to 20.2 percent.

“The pattern is definitely meaningful, but like the effect itself, we don’t really know what the lesson is yet,” Huffington Post senior polling editor Natalie M. Jackson told the Washington Examiner on Monday.

Trump’s competitors aren’t surprised by this disparity. They believe it’s legitimate; it’s among the reasons why they are more optimistic about their prospects than might be expected given that Trump has led in most state and national polls since July, except for a recent period when it appeared he had been dethroned by Carson. Senior advisers to rival GOP campaigns say the polling has been influenced by several unique factors, including faulty methodology.

The blanket coverage of Trump on cable television news stations has obscured the rest of an otherwise deep field of contenders. When asked in polls why they are supporting Trump, many voters have said that they haven’t heard anything about the other candidates. That has begun to change with in uptick in advertising by, and media attention on, other candidates. This change could have a major impact on the race in the days ahead.