The dog that didn’t bark in the midterm elections was the U.S. economy. Normally, it’s the top issue voters worry about. But not this year.

If that’s also the case in 2020, President Trump’s reelection odds ought to be pretty good. Trump’s Republicans lost control of the House of Representatives on Nov. 6, but they lost fewer seats than normally happens for a president whose approval rating is below 50%, as Trump’s is. And they appear to have gained 4 seats in the Senate, when the normal midterm outcome is a net loss for the president’s party. Despite losing the House, Trump and the Republican Party outperformed this year.

The strong economy is a big reason why, and that foretells a key factor for the 2020 presidential race. If the economy remains strong, it would obviously benefit Trump. But if there’s a palpable slowdown or a recession by then, Trump will probably lose a sizable chunk of his support, opening the door to a Democratic challenger and perhaps a sweep of Congress.

Forecasters knew well before the election that the economy was a net positive for Trump and his fellow Republicans. Normally, voters say the economy is their top concern, which is why Bill Clinton’s famous mantra in the 1992 election was, “It’s the economy, stupid.” That has generally been true ever since.

Health care is top of mind

But exit polls show that wasn’t true this year. In CNN exit polls, voters said health care was the top issue, followed by immigration. The economy came in a fairly distant third. While 41% identified health care as the top issue, only 22% fingered the economy.

There’s a huge partisan split, as anybody following politics knows. Of those saying health care is the most important issue, 75% were Democrats and only 23% were Republicans. Of those saying immigration is most important, it’s the exact opposite. Of those saying the top issue is the economy, 34% are Democrats and 63% are Republicans.

But some voters who say the economy is the top issue apparently mean that a strong economy is what they care about. Sixty-eight percent of voters this year said the national economy is “good,” with only 30% saying it’s “poor.” Just two years ago, views were very different. In 2016, just 36% of voters said the economy was good, while 62% said it was poor.

The main takeaway is that the strong economy probably kept some Independent voters in the Republican column, and may have persuaded others to stay home instead of casting a protest vote for Democrats. There are always some voters who punish the incumbent president and his party if the economy is shaky, and they were not much of a force in 2018.