Of all the market-moving tweets these days, one in particular from Democratic presidential hopeful Sen. Elizabeth Warren is sending shivers through the oil industry.

“On my first day as president, I will sign an executive order that puts a total moratorium on all new fossil fuel leases for drilling offshore and on public lands,” she tweeted on Sept. 6. “And I will ban fracking—everywhere.”

Outlawing a technique that energy producers use to blast oil and gas from shale formations would require legislation and spur a torrent of opposition from companies, investors and probably even state governments.

Substantial as those hurdles may be, they haven’t stopped analysts from running the numbers for investors and energy executives to see what might happen, if hydraulic fracturing were banned.

They are particularly focused on Ms. Warren’s threat to choke off drilling on federal lands.