Speaking to a crowd of supporters in Wisconsin this week, President Trump assured them that his presidency was reshaping American politics in at least one significant way.

“There’s never been a movement like this, never happened before, but we’re a movement for all Americans who believe in fairness and justice, equality and dignity, opportunity and safety,” Trump said. “We are a big tent, and we are a big party of big ideas for the future.”

“And that’s why African Americans are joining the Republican Party like nobody ever thought even possible,” he continued. “They love us and we love them.”

He went on to give an example of how he had helped black Americans: signing into law reforms to the criminal justice system that, he said, had “helped so many people, especially in the African American community, the Hispanic community.”

Trump’s claim (if not the evidence he presented for the claim) is hard to square with a new Post-Ipsos poll showing that more than 4 in 5 black Americans think the president is racist. Nine in 10 disapprove of the job he’s doing, the sort of numbers that do not suggest much “love” for Trump. Three-quarters of black Americans think that his presidency is bad for their community.

So who’s right, Trump or, you know, objective data? Well, the data, as you might expect — but Trump’s claims about shifts in the black vote do, perhaps inadvertently, get at a recent shift in American politics.

Black Americans have been strong supporters of the Democratic Party for more than half a century. That’s a shift from the first half of the 20th century, when black Americans were largely split between the parties.

What happened? Democratic presidents embraced and advocated legislation aimed at bolstering the civil rights of black Americans. First, in 1948, Harry Truman pushed Congress for new laws protecting voting and banning lynching. Then, in 1964, Congress passed the Civil Rights Act, which President Lyndon B. Johnson signed into law. Since, black Americans have overwhelmingly supported the Democratic Party.

We can see that in recent years that support hasn’t changed much. Data from Pew Research Center show that the percentage of black Americans who identified as Republicans or Republican-leaning independents dropped a few points from 2015 to 2016, though not to a statistically significant degree. From 2016 to 2017, the change was similarly flat.

In other words, no apparent big surge to the GOP among black voters — at least through 2017.

As it stands in the most recent set of national registration data compiled by the political data firm L2, more than 8 in 10 black Americans are Democrats. (Some of these data depend on imputed determinations of party or race.) The black population is heavily centered east of the Mississippi; the density of party registration varies from state to state.

In part thanks to the loyalty of black voters, the Democratic Party is much less heavily white than the Republican Party, according to Pew data. About 6 in 10 Democrats are white, compared with more than 8 in 10 Republicans who are white. The Democratic Party was more diverse in 1997, in fact, than the GOP is today.

About 2 percent of the GOP is black, compared with about 20 percent of the Democratic Party. Another 20 percent of the Democratic Party is Hispanic, Asian or members of another nonwhite group.

As a result, the nonwhite vote makes up an increasingly important part of the Democratic electorate in presidential races, according to exit polling.

Notice, though, what happened in 2016 relative to the years prior. While the nonwhite vote made up a higher percentage of the Democratic vote in 2016 than in 2012, the black vote made up a smaller percentage of it.

Why? In part because turnout among black voters dropped from 2012 to 2016. Analysis of the 2016 election completed by a group of data scientists showed that 11 percent of blacks who had voted for President Barack Obama in 2012 stayed home four years later. That, combined with the 12 percent of white Obama voters who flipped to Trump, was likely key in the outcome.

In fact, more than a third of those who didn’t vote in 2016 after backing Obama four years prior were black, according to the same analysis.

What happened? Well, one thing, certainly, was that the first black president was not on the ballot. Black turnout in 2016 was about where it had been in 2004.

If we compare self-identified party affiliation from the General Social Survey in four-year increments relative to the total identification from 2000 to 2018, we see a sharp shift among black respondents. From about 2000 to 2014, black respondents were more likely to identify as Democrats than they did broadly over those 18 years. (This fluctuates up and down with more identification with the party in presidential years than off-years, so we averaged the two results as indicated on the bottom axis.) In the 2016 and 2018 surveys, black respondents were on average about six percentage points less likely to identify as Democrats than they were over that whole 2000-2018 period. Again, part of this is likely a function of the Obama presidency boosting party loyalty, but it’s still a notable shift.

But notice where there were gains: Among those who identify as independents, either independents leaning toward a party or pure independents, black respondents were also less likely to identify as Republicans in the average of the 2016 and 2018 surveys than they were on average over the 2000-2018 period.

That’s a broader trend in American politics, of course, the shift from parties to identifying as independents. The state-by-state map from L2 above shows a number of places where, while there aren’t many black Republicans, there are sure a lot of black independents.

The L2 data also suggest that there’s a generational difference. No age group of black voters is particularly likely to identify as Republican, but younger black voters are more likely to identify as independent or third party.

That’s a broader question — 1968 was more than 50 years ago. That oldest group of 70 and older black voters was of voting age when the bill passed. They are also the most heavily Democratic. Black Americans younger than 50 have never known a pre-Civil Rights Act America — and they are also less likely to identify with the party whose president brought that bill to fruition.

So the evidence doesn’t support Trump’s claim that black Americans are being wooed by his policies to vote Republican. There are, instead, larger trends that are creating space between black voters and the Democratic Party — trends that may have contributed to a drop in turnout in 2016 and, therefore, to Trump’s election.

Trump’s sharp unpopularity with black voters is a bad sign for him this year, it would seem. (There’s no difference in disapproval for Trump by age in our new poll, for example.) A more interesting question, then, may be what happens in the first, post-Trump election, one in which there’s a Republican who is perhaps viewed with less skepticism by a more independent bloc of black voters.