WASHINGTON — Politics have been at the center of the public debate about the Justice Department’s lawsuit to block AT&T’s $85 billion purchase of Time Warner. But the trial itself, starting later this month, is shaping up to be a fight focused on classic issues in antitrust law.

In court filings on Friday, the Justice Department and AT&T laid out the arguments that they plan to make in the trial. Regulators will argue that the deal will hurt competition and lead to higher prices. AT&T and Time Warner will counter those arguments by saying that even with a merger, it is an underdog against online giants like Facebook and Google.

“If TV-program distributor AT&T acquires TV-program producer Time Warner, American consumers will end up paying hundreds of millions of dollars more than they do now to watch their favorite programs on TV,” the Justice Department said in its brief submitted on Friday evening.

In its brief, AT&T countered by saying, “This merger has never been about making Time Warner programs less accessible or more expensive. Just the opposite: It is about making Time Warner and AT&T more competitive during a revolutionary transformation that is occurring in the video programming marketplace.”