When President Trump addresses the nation on Tuesday evening to make the case that migrant crossings at the U.S.-Mexico border constitute a crisis, he won’t have to convince his supporters of the need to build the wall he has long promised. Since Trump is trying to get the rest of the country onboard, his critics are arguing that the address should be seen as a de facto part of the 2020 presidential election campaign.

In a joint statement on Monday, House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles E. Schumer (D-N.Y.) said they should receive equal airtime after Trump’s TV address. The two Democratic leaders voiced concerns that Trump could again use his address to spread “misinformation.” Immigration scholars similarly have pointed out that the Trump administration has misled the public on the security threat posed by border crossings multiple times, for instance by exaggerating numbers.

Under the so-called equal time rule, U.S. broadcasters are already required to provide political opponents equal airtime if they so desire, but there are now so many exceptions to this law that it rarely determines who gets on the air and who doesn’t. And then there’s the question of when U.S. election campaigns actually start, or if they ever really end.

There are measures in place to allow the opposition party to offer prominent rebuttals in Congress to a president’s perhaps most important regular speech, the State of the Union address. But those efforts do not extend to broadcasters.

It looks likely that Pelosi and Schumer will receive the airtime they have requested. But what would happen if that were the norm rather than the exception?

While enforcing a real equal airtime rule might sound impossible to keep track of or even in contradiction with freedom of expression, there is some substantial data on how it could play out. Some European countries have long relied on airtime laws to prevent media bias — and while the restrictions there have tended to encourage a more serious political discourse, things can easily become messy.

France is perhaps the most prominent case study. Once election campaigns officially start in Paris — with a few weeks to go until voting day — French broadcasters are required to give all presidential candidates the same airtime. A previous version of the law stated that airtime should be based on a candidate’s rating in the polls, but with pre-election surveys perceived as increasingly inaccurate, lawmakers recently opted for equal airtime for all.

While the number of weeks this rule applies ahead of elections was recently cut down from five to two, the law is taken much more seriously in France than in other countries. Unlike in the United States, it is also enforced during newscasts, which still tend to attract tens of millions of viewers every day. Not complying isn’t really a possibility: Ahead of a presidential election two years ago, France’s media supervisory authority tasked more than a dozen employees with monitoring radio stations and TV broadcasters to measure every second of coverage.

Additionally, French broadcasters are prohibited from broadcasting political campaign ads, to prevent wealthy donors from being able to shift the political discourse. Similar rules apply in other European countries, including Belgium and Ireland. Meanwhile, the United States has gone in the other direction with the Supreme Court’s 2010 Citizens United decision stating that restricting third-party campaign ads limits free speech.

The European approach gained some support during the 2016 presidential election campaign in the United States, when cable networks dedicated much of their airtime to a candidate initially considered unlikely to win. While there is disagreement on the type of content that really counts as “coverage,” media measurement firm mediaQuant found after the U.S. elections that cable networks’ focus on Trump had provided him with free publicity worth $5.8 billion in advertising. Democratic rival Hillary Clinton received only roughly half of that.

In much of Europe, such a skewed media focus would simply be against the law. Britain’s public broadcaster, the BBC, for instance, reaches huge audiences and is respected across the political spectrum. Its supporters agree that this is due to its efforts to always include commentary from both sides of the political spectrum, ideally for the same amount of time. The British rules have triggered more criticism in the recent months of Brexit negotiations, as the broadcaster has been accused of providing politicians with a platform to repeat inaccurate statements, rather than debunking or disinviting them, but the BBC standard is still seen as a more flexible alternative to the strict French government-controlled approach.

The French rule has also faced a fair share of criticism but not for reasons that would necessarily apply in the United States. In Paris, broadcasters have complained about the need to dedicate airtime to as many as 11 candidates with days to go until elections, even though the majority of them have almost zero chance of winning. They argue that the rule unnecessarily distracts from high-profile issues that voters would like to hear discussed. In a recent letter of complaint, they also wrote that the legislation forces them to broadcast less political coverage to keep ratings at a stable level, as bored viewers move on to coverage of more relevant candidates online or on other channels.

While those concerns may be somewhat justified for a presidential election debate with 11 candidates, that’s less valid in the U.S. system where only two candidates end up having a chance to win.

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