President Trump gives thumbs up after stepping off Marine One on the South Lawn of the White House on May 17 in Washington. (Alex Brandon/AP)

On the face of it, Quinnipiac University’s new poll measuring support for President Trump’s reelection bid is bad news for the incumbent: More than half of respondents said they will definitely not vote for Trump in 2020. Only about 3-in-10 respondents said they definitely will.

(Philip Bump/The Washington Post)

How does that compare to other recent presidents? Allow CNN’s Harry Enten to explain.

But Trump and his supporters have a counter to this: The economy is so good and things are going so well with employment that Trump’s reelection should be the default assumption. Trump himself suggested on Wednesday morning that his approval numbers were artificially low because of the Russia investigation. Barring that, Americans would actually support him at much higher levels, he claimed, because of the health of the economy.

I get why he says that. Historically, economic data has correlated to support for the incumbent party. A better economy, a more popular president, a better chance of reelection. But it’s not quite that simple, especially now, in this very polarized moment, and especially with Trump, a very polarizing president.

Quinnipiac provided The Washington Post with a breakdown of how support for Trump’s reelection varies depending on how people view the economy and his handling of it.

Take the question of whether people approve of Trump’s handling of the economy. Views are mixed, with about half of respondents saying they approve and half saying they don’t. Of those who disapprove of Trump’s handling of the economy, nearly all said they definitely won’t vote for him. Among those who approve, 6 in 10 said they would.

(Philip Bump/The Washington Post)

But among those who approve of his handling of the economy, more than a third said either that they might vote for him or that they definitely wouldn’t. So if Trump’s claim is that the economy will power his election, it’s worth noting that at least a third of those who already give him points on that front still waver on giving him their support.

The picture is slightly better on Trump’s handling of trade. There, those who approve of what Trump’s doing are 10 points more likely to say they’ll definitely vote for him. But this group is also 10 points smaller than those who approve of his handling of the economy (39 percent vs. 48 percent). Meaning that it’s probably a group that’s more densely Trump’s base.

(Philip Bump/The Washington Post)

That raises an important point: Much of the support for Trump’s moves on economic issues is driven by support for Trump — just as much of the opposition to Trump’s economic moves is driven by opposition to Trump. The president claims that the latter group is movable, but he seems to think that the former group doesn’t really exist, that support for him is generated by support for what he’s doing and not vice versa.

Things get more interesting as we get closer to home. Quinnipiac also asked respondents if their own financial position had gotten better or worse since 2016. About half said things had gotten better — but more than a quarter of that group said they plan to vote against Trump anyway.

(Philip Bump/The Washington Post)

Overall, among those who’ve seen their financial fortunes improve, results were about split between those who definitely plan to vote for Trump and those who might not or definitely won’t.

And this is on the central component of Trump’s argument! He and his supporters claim that the health of the economy will spur support for his candidacy. The Quinnipiac poll suggests that this may be overly optimistic.

We don’t have to rely just on that poll. Shortly before the midterm elections, Gallup released a number of data points related to past midterm elections. Among the comparisons was a look at how voters’ views of the economy affected the results of the off-year contests.

We took that data and made a rough forecast for what the (limited) data suggested. Given how much confidence people had in the economy, past precedent suggested that the Republicans (the president’s party) would only lose a handful of seats.

They lost 41.

(Philip Bump/The Washington Post)

Gallup also released data on presidential approval. Those data suggested that the loss for the GOP would be about 39 seats — far, far closer to the mark.

(Philip Bump/The Washington Post)

The lesson from those data was clear: When it came time to vote in 2018, dissatisfaction with Trump was a better predictor of the result than the health of the economy. It’s sort of the flip side of the coin shown in the Quinnipiac poll: Even those with confidence in the economy aren’t sold on Trump.

And if Trump doesn’t have the economy to woo voters who aren’t in his base, what has he got?