“I personally think that when people see the details, they will hesitate,” he said, referring to the complexity of any deal Mrs. May can negotiate.
Many would dispute that assertion. And thanks in part to his active role in pursuing the Iraq war, Mr. Blair is a diminished figure in Britain these days, particularly within his Labour Party, which has swung to the left.
But his skill in winning elections is undisputed. Capturing the political center ground, Mr. Blair was elected prime minister in May 1997, becoming, at 43, the youngest premier since Lord Liverpool in 1812, ending 18 years of Conservative government and sparking the optimistic “Cool Britannia” era.
Mr. Blair also later secured two more victories. Yet the Conservatives are now firmly back in power, and the Labour Party is led by Jeremy Corbyn, its most left-wing leader in decades, who trails Mrs. May badly in opinion polls.
Citing polls in Britain suggesting that Mrs. May will win in June, Mr. Blair urged Britons to vote for candidates who want to keep options open on Brexit, provide an opposition and deny Mrs. May a “blank check.”
Despite the aftershocks of the financial crisis, Mr. Blair believes that centrists can find answers to globalization. He described Emmanuel Macron, a contender for the presidency of France, as a force for change in Europe.
The key, Mr. Blair said, is “accepting globalization as a fact, accepting its benefits but preparing people for its consequences,” rather than embracing protectionism or isolationism.
Speaking in his London office on Friday, Mr. Blair said he would “never give up” on the idea of remaining in the European Union, though he conceded that others think is this now impossible.
One theory about the coming elections is that, if Mrs. May wins a significant parliamentary majority, she will gain the political space to compromise, and retain close ties to the European Union.
But Mr. Blair thinks she is headed in the opposite direction, appealing to supporters of the U.K. Independence Party, or UKIP, a right-wing, anti-European Union party, and to Labour voters who opted for leave the union.
“They’re collapsing the UKIP vote into them, and they’re going after the Leave vote from Labour,” he said, sipping coffee (which he gave up while prime minister). “Now that doesn’t strike me as a strategy designed to give you an easier ride on Brexit.”
As for the timing of the election, he said it was “the optimal moment for Theresa May to say, ‘Give me the strong mandate’ before people actually know what this negotiation means.”
When they realize the implications, Mr. Blair said, attitudes may shift. “All I say to you is it was 52 percent to 48 percent,” he said, referring to the…