Go deeper: The U.K. is changing its mind on Brexit

More than 25% of the 403 constituencies of British Parliament that voted to leave the European Union in 2016 now oppose Brexit, according to data reviewed by The Guardian.

The big picture: The majority of parliamentary seats now favor remaining in the EU, a shift driven largely by members of the Labour Party in northern England and Wales who originally voted to leave. But even if attitudes hadn't changed, analysis shows that trending demographic changes in the U.K. would be significant enough to reduce support for Brexit by 2% in 2019, 4% in 2021, and more than 7% in 2026.

The backdrop: In June 2016, citizens of the United Kingdom voted by a 51.9%-48.1% margin to leave the EU.

• A study by NatCen Social Research found that the vote crossed over party lines, and that those most likely to choose "Leave" had little formal education, low incomes, and often lived in public housing.
• Older white voters who viewed themselves more as "English" than "British" and believed Britain had gotten "a lot worse" in the past decade were also among those most likely to vote Leave.

"The Leave victory was not about demographics alone, though it is clear that age, levels of education, income and newspaper readership are all related to the likelihood of voting Leave. Matters of identity were equally, if not more strongly associated with the Leave vote – particularly feelings of national identity and sense of change in Britain over time."

Between the lines: The main voting cohorts who chose Leave — including uneducated white and British-born voters who grew up before Britain joined the EU — all are shrinking in size, while their Remain-leaning counterparts are growing, according to an analysis by the London School of Economics.

• For the past three decades, the number of college graduate voters in the U.K. has risen by .7% each year, while those with no formal education has dropped by 1%.

• Ethnic minorities have also greatly increased and are on average younger than the U.K.'s white population.
• Turnout in the 2016 Brexit referendum was dominated by "eurosceptics" who grew up before Britain joined the EU, but mortality will soon tip the electorate toward younger, more pro-EU generations.

The bottom line: The trending direction of the average British voter as it relates to education level, ethnic identity and formative experience spells trouble for pro-Brexiteers, especially as the struggle to strike a deal with the EU prompts calls for a second referendum.