Good overview of the tone and substance of recent political discourse in Britain:

As Britain engages in fierce debates centered on national identity, it is also confronting challenges to traditional norms of political discourse, with issues of race and religion surfacing more overtly and provocatively.

The looming referendum on whether to leave the European Union, the place of Muslims in British society at a time when Islamic terrorists are targeting Europe, the broader question of the island nation’s openness to immigration and the Israeli-Palestinian conflict all have recently sparked controversy and heated commentary about discrimination and tolerance.

Like most European countries, many of which are facing growing populist movements on the far right, Britain has always grappled with a strain of racial and religious bias. But the political calendar and global events have combined to push the topic to center stage.

President Obama, during his three-day visit here that ended on Sunday, was the focus of an extraordinary squabble that centered on his Kenyan father and attitudes toward British imperialism.

Boris Johnson, the Conservative legislator, mayor of London and leader of the campaign against British membership in the European Union, responded to Mr. Obama’s robust call for Britain to stay in the bloc with an opinion piece centering around Mr. Obama’s removal of a bust of Winston Churchill from the Oval Office.

Mr. Johnson suggested that Mr. Obama may have been motivated by “the part-Kenyan president’s ancestral dislike of the British Empire, of which Churchill had been such a fervent defender.”

That comment provoked furious claims that Mr. Johnson, often mentioned as potential successor to Prime Minister David Cameron as leader of the Conservatives, was making a smear based on Mr. Obama’s race in order to undermine his arguments in favor of Britain remaining in the bloc.

Britain’s foreign secretary, Philip Hammond, told the Telegraph icily about Mr. Johnson: “People who aspire to hold offices of great responsibility do have to show that even under pressure they retain their cool and they don’t step over any red lines.”

Mr. Obama neatly parried the thrust without responding in kind, saying that he thought even Britons would understand that he might find it “appropriate” to have a bust of the Rev. Dr. Martin Luther King Jr. instead.

But the dispute touched deeper chords here about whether Britain can better control its borders and defend itself from terrorism from within or outside the European Union. Mr. Johnson argued that Mr. Obama is “hypocritical,” saying the United States would never cede such control over its sovereign borders to anyone.