But less than two years after Scots opted to remain in the United Kingdom, the specter of secession again looms over the lush green expanse of the British isles. The trigger this time is another referendum with existential impact: next month’s vote on whether to leave the European Union.

If Britain chooses to ditch the E.U. despite a vote to stay from the Euro-friendly Scots, nationalist leaders here say they will revive the push for an independent nation in order to keep Scotland inside Europe. And they think that the second time around, they would win.

“Pulling Scotland out of the European Union against our will would be a change in material circumstances,” said Alex Sal­mond, who led the campaign for independence in 2014 and now represents Scotland in the British Parliament.

In that scenario, he said, there will be “a referendum on Scottish independence within the next two years. And this time, the result would be ‘yes.’ ”