The biggest media news this year has been the mega-merger of Sinclair Broadcast Group and Tribune Media, which would create the largest broadcast company in history—if antitrust regulators approve the deal. Republicans have been largely supportive of the move, not just because of the principle that the government should stay out of business decisions, but also for political reasons: Conservatives are excited about the prospect of a national broadcast giant with a distinct right-leaning perspective.

In the short term, they’re right to be excited: The merged broadcaster would have 215 TV stations covering more than 72 percent of U.S. households, an unprecedented reach into Americans’ living rooms. But in the long run, the move could well backfire, creating huge political problems for Republicans and President Donald Trump. Opening the door to the Sinclair deal could pave the way for networks such as NBC, CBS and ABC to consolidate their own empires even further, creating huge liberal broadcasters that dwarf the size and power of the merged Sinclair-Tribune company.

In many ways, the conservative revolution owes its early success to the ownership limits placed on big liberal media companies. When Ronald Reagan won the presidency in a 1980 landslide, many credited his win on restrictions against the liberal media’s ability to own most of the local broadcast TV stations throughout the United States. At that time, a single entity could only own seven broadcast television stations. Compare that to the 200-plus stations Sinclair will own if this transaction is approved. Then-candidate Reagan was able to reach America through a diverse group of broadcast owners, bypassing the liberal bias of New York City network executives at NBC, CBS and ABC.

It’s clear that Reagan understood the critical importance of local media diversity: During his first term, the Federal Communications Commission raised the limit of stations a company or individual could own from 7 to 12, but it imposed a 25 percent cap on the number of TV stations a single network could own nationwide.

The value of the FCC ownership cap was evident just a few years later. In 1994, when Newt Gingrich and I helped lead the first Republican takeover of the House of Representatives in a half century, we were able to share details of our Contract with America and spread our message of limited government and individual rights. At the time, we made a point of ignoring the large New York-based networks, and instead cultivated relationships with local TV stations and other media outlets. Had a merger like Sinclair’s been approved before 1994, and liberal networks like NBC could own stations reaching up to 72 percent of U.S. homes, I doubt we would have won.

Decades later, Trump directly benefited from this wide distribution of ownership. He was able to connect directly with voters in states like Ohio, Michigan and Wisconsin, which have very few, if any, local TV stations owned by the major TV networks.

Don’t get me wrong: I appreciate the conservative perspective of Sinclair and support its First Amendment right to espouse its views. We should tread carefully when regulations could limit speech. But the spectrum Sinclair utilizes to broadcast is limited and this transaction would set a terrible precedent by opening the door for ABC, CBS, and NBC to also buy many more TV stations. At that point, nothing can stop liberal Northeast corporate executives from telling homes in the heartland what to think.

In addition, forcing Sinclair to sell off a handful of TV stations in markets where it already has a broadcast license doesn’t solve this problem. It’s merely window dressing. Even after those divestitures, Sinclair would still reach about 70 percent of U.S. TV households. The result is the same: The administration would be powerless to stop further anti-competitive media consolidation.

For Trump, there’s another big reason to block the Sinclair-Tribune merger: It would undermine the Department of Justice’s current challenge against a much more important merger—the $85 billion deal between AT&T and Time Warner—while giving Democrats a rallying point to use in the 2018 midterms.

Right now, the Trump administration is suing AT&T and Time Warner, which owns CNN, in an attempt to block what many believe would put “too much power in the hands of too few,” as then-candidate Trump said during his 2016 campaign. Yet the Sinclair deal clearly poses a far greater economic threat than the AT&T-Time Warner deal, since Sinclair’s national reach will lead to higher rates for advertisers, as well as for cable and satellite TV subscribers.

By giving Sinclair a free pass, Trump’s DOJ would be gifting AT&T’s lawyers with a powerful argument that DOJ’s selective enforcement is not only arbitrary but also illogical: AT&T-Time Warner poses a risk to consumers and competition, but Sinclair-Tribune does not? Judge Richard J. Leon, who is overseeing the AT&T-Time Warner case, is sure to ask: “What’s going on here?”

Approving the Sinclair deal while challenging the AT&T-Time Warner merger would also give an easy talking point to liberal Democratic senators who have claimed that the DOJ lawsuit is political payback for CNN’s drumbeat of anti-Trump news. Whether true or not, if Trump’s DOJ rubber-stamps the Sinclair-Tribune deal, Democrats would use it to rally their base in 2018, alleging that Trump is abusing his position by using the government’s antitrust enforcement powers to punish his enemies and help his friends.

For the sake of the conservative movement, a truly diverse press, and real competition, the DOJ should stick to Trump’s campaign promise to protect the public against the “concentration of media power” and reject the Sinclair-Tribune merger. We simply have too much to lose.

Tom DeLay represented Texas as a Republican in the U.S. House of Representatives from 1985 to 2006 and served in House Republican Leadership from 1993 until 2005.