The allegations are explosive: Ajit Pai, President Donald Trump's hand-picked head of the main U.S. media regulator, has been changing regulations to fuel the expansion of a right-wing, pro-Trump media giant across the U.S.

If true, the actions would represent nothing less than a major corruption scandal with the goal of pushing pro-Trump media to millions of Americans without them knowing.

The evidence? Well, it's been laid out by 13 Democratic senators who are calling for an investigation. They allege that Pai, head of the Federal Communications Commission (FCC), which governs media ownership in the U.S., has changed important rules in order to allow Sinclair Broadcasting—a quiet giant in U.S. media, particularly around local TV—to expand significantly.

Sinclair is well-known in media and political circles for having a strong conservative slant and maintaining a cozy relationship with Trump. The company has required its stations to run segments from a former Trump administration official who is now a political commentator for Sinclair. Sinclair agreed to acquire Tribune Media and its 42 local TV stations for $3.9 billion in May. Chances are, if this deal goes through, you will have a Sinclair station broadcasting in your hometown, if you don’t already.

It's Pai that the Senate Democrats want investigated by the inspector general of the FCC. In the letter, Trump's interaction with Sinclair executives are chronicled, leading to the appointment of Pai, who then also repeatedly meets with Sinclair executives while also making changes to FCC rules that paved the way for Sinclair's acquisition of Tribune to be approved. It's a smaller deal in terms of dollars compared to the Time Warner/AT&T deal, but is arguably bigger in terms of the impact on the average American and their news consumption.

"We write to request that you commence an investigation into whether the chairman of the Federal Communications Commission (FCC), Ajit Pai, is executing his leadership of the FCC free from influences that compromise his objectivity and impartiality," reads the letter, signed by the 13 senators and sent to David Hunt, FCC inspector general.

The senators included a damning timeline of communications and meetings between Trump, Sinclair and Pai, with 16 instances that highlight how the Trump administration grew cozy with Sinclair and then had the FCC start changing rules to allow them to acquire Tribune Media. That deal would make Sinclair a behemoth in local TV, reaching 72 percent of U.S. households, according to the letter.

NEWS: Led by myself & @SenatorTomUdall,13 @SenateDems are calling for impartial investigation into potential quid pro quo between chairman @AjitPaiFCC, the Trump Administration & #Sinclair broadcasting. READ our letter to the @FCC Inspector General pic.twitter.com/B0oI2HMPIg — Sen. Maria Cantwell (@SenatorCantwell) November 15, 2017

"Put simply, this timeline suggests a disturbing pattern of a three way quid-pro-quo involving Sinclair, the Trump Administration, and Ajit Pai. Because of these facts, we are gravely concerned that Chairman Pai may have engaged in a pattern and practice of activity related to the Sinclair-Tribune transaction in a way that imperils the independence and public interest mission of the FCC," the letter states.

The FCC is the primary government agency charged with regulating the U.S. media industry. Over the years, they've put a variety of rules in place; some prevent companies from getting too big, others ensure media companies have some stake in the localities in which they operate.

The FCC is run by five commissioners, one of whom is the chairman, who generally leads the organization and dictates its agenda. The president appoints the commissioners and generally puts in place a majority sympathetic to the president's party.

Trump appointed Pai, who had served as a Republican commissioner under Barack Obama. He was known for being a charismatic figure, though one that was aggressively anti-regulation. Pai has also moved to dismantle the strong net neutrality protections put in place under Obama.

A spokesperson for Pai responded to a request for comment by slamming the accusations: "This request is absurd on its face and nothing more than a last-ditch attempt by those desperate to block innovation in the broadcast industry and modernization of the FCC’s outdated broadcast ownership rules."

The letter doesn't come out of nowhere. Two Democratic members of the House of Representatives have been pushing for more information about Pai's relationship with Sinclair, but their demands have been ignored. They also recently issued a letter calling for an investigation by the FCC inspector general.