Steve Bannon, the mercurial mastermind behind Donald Trump’s presidential campaign, has come under fire in recent weeks. Bannon, now serving as chief presidential strategist, has openly feuded with Trump’s senior adviser (and son-in-law) Jared Kushner. Tensions, reportedly, have reached a tipping point, and Bannon may be close to losing his job.

If Trump does decide to part ways with Bannon, however, he might pay a steep political price. Bannon is a bomb-thrower, and a very well-financed one at that. His influence will not end at the doors of the White House. Released back into the media wild, he could mobilize a significant portion of Trump’s base against him.

To appreciate how troublesome a liberated Bannon could be to Trump’s presidency, it helps to understand his long-standing alliance with Robert Mercer, the billionaire financier behind Breitbart.com, Trump’s campaign, and a host of hard-right advocacy groups.

Jane Mayer profiled Mercer recently for the New Yorker. Last week, she and I talked about Mercer’s deep ties to Bannon and the broader conservative media.

She explained how Bannon could unleash political hell on Trump if he’s cast out of the White House and returns to the media world:

What the Mercers did, with the guidance of Steve Bannon, was not just fight the press — they tried to supplant mainstream media. They invested $10 million or so in Breitbart News, building it into a formidable platform for economic nationalism, and they put millions into creating and funding the Government Accountability Institute, which provided their own politically potent content to the mainstream press.

This alternative media ecosystem remains intact, and, as Mayer points out, it can — and likely will — turn on Trump if he fires Bannon and surrenders to the more centrist Kushner camp:

It’s unclear how much this operation will “box-in” Trump now. Bannon says he has severed ties to Breitbart while serving in the White House. But whether or not Bannon is actively involved, Breitbart continues to exist as a political force, funded by the Mercers, and ready to hammer Trump when he diverges from their political agenda, as it did when opposing the Ryan/Trump health care plan.

The New York Times’ Jeremy W. Peters and Maggie Haberman report that Rebekah Mercer, the daughter of Robert Mercer, is already “discussing possibilities for Mr. Bannon should he leave” the Trump administration. It’s not yet clear what those possibilities are, but they might very well include using the Bannon-inspired media empire to punish Trump for perceived betrayals.

You can read my full interview with Mayer here.