President Joe Biden speaks before signing the Democrats' landmark climate...

President Joe Biden speaks before signing the Democrats' landmark climate change and health care bill in the White House in Washington on Aug. 16. Credit: AP/Susan Walsh

Lots of things are broken right now in U.S. politics. The good news is that there's new evidence that one important thing is working just fine: When bad things happen presidents get less popular, and when good things happen? Their approval ratings improve.

Six weeks ago, President Joe Biden's approval ratings were falling rapidly. That continued into July, eventually reaching a low point of 37.5%, according to FiveThirtyEight. He's recovered a fair amount, gaining three percentage points over the last 30 days.

No one can prove why Biden's numbers have bounced back, but two major drags on American life during his presidency — gas prices and COVID-19 cases — are finally dropping at the same time in recent weeks. Jobs, meanwhile, remain strong while overall inflation is still high, but tailing off. As a result, overall perceptions of the economy are rising.

There have been other positive developments in the news — including some Biden is more directly responsible for — but the history of approval ratings suggest that they are less likely to be affected by passing bills and signing them into law.

All of this is very good news about the political system. While it seems obvious, it's a health sign for our politics system if positive news makes presidents more popular, and negative news makes them less popular. And there's been a lot of speculation otherwise.

Donald Trump's approval ratings didn't usually react that way. Even when perceptions of the economy were excellent, Trump never managed to reach as high as 50% approval. After his first several months, his approval ratings refused to move much for good or bad news.

To some analysts, it looked like sharpening partisan polarization was ushering in a new era of presidential politics. Views of the president would depend on partisanship, not the actual state of the union. If true, then presidents would no longer have a strong electoral incentive to produce results that made voters happy.

As long as presidents and their party have strong incentives to produce positive results and to avoid doing things that would make voters unhappy, the basic structure of democracy should, over time, tend to have good outcomes. That's a big deal!

Meanwhile, it's obviously good news for Biden and the Democrats that he's rebounding from his low point, but it's still very unlikely he'll recover enough in time to help his party in the midterms. Historically, the president's party will almost certainly get clobbered if that president's approval rating is below 45%, and Biden's going to have to keep gaining to come close to that level. After 576 days, there are still only two presidents in the polling era who had worse numbers: Harry Truman and Jimmy Carter.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners. Jonathan Bernstein is a Bloomberg Opinion columnist covering politics and policy. A former professor of political science at the University of Texas at San Antonio and DePauw University, he wrote A Plain Blog About Politics.