NEW YORK (Reuters Breakingviews) - Donald Trump just gave Joe Biden a gift. The first televised debate of the 2020 election could have forced the Democratic presidential nominee to explain how he can appease both economic moderates and progressives. The anarchic behavior of the sitting president rendered that unnecessary. Tuesday’s debate was a train wreck from the get-go. The moderator, Fox News Sunday’s anchor Chris Wallace, quickly lost control as the president refused to stop interrupting. The debate included questions on topics ranging from the Supreme Court to the integrity of the elections, but the 90 minutes included little substantive discussion, and the near-constant heckling of Biden by Trump. The former vice president has had to appeal to a very broad church. While he’s still essentially a centrist, as his party has shifted left, so has he. Biden is calling for a $15 an hour minimum wage, an expansion of government-assisted healthcare and free tuition at public college and universities for families earning under $125,000. This is far from a radical turn – but it does create a vulnerability. Trump has focused attention on Biden’s more liberal allies, whom he brands the “radical left.” In reality, Biden has walked a fine line. He hasn’t personally endorsed New York Representative Alexandria Ocasio-Cortez’s call for a 70% marginal tax rate, say. Or Senators Elizabeth Warren and Bernie Sanders’ plea for a wealth tax. Trump could have tried to box Biden into an ideological corner – especially on economic issues. Over half of Americans still approve of the president’s handling of the economy despite the over 8% unemployment rate. But his feeble attempts to do so – including references to socialism within the first 15 minutes of the debate – were cartoonish. The moderator did push Biden on tax increases and spending priorities like fighting climate change. But the nominee was mostly able to reframe the question, in one instance focusing on corporates that pay little in tax. When necessary, he was able to separate himself from bolder progressive ideas, like the multi-trillion-dollar Green New Deal or the campaign to defund the police, without appearing to discredit their supporters. While the debate could have dug deeper into Biden’s ideological conflicts, it ultimately presented voters with a choice, between something-like-normality or chaos. The Democratic contender should be thankful that Tuesday night was, in the end, all about Trump.