John Cassidy in The New Yorker:
It would be uplifting to report that since the referendum, in June, which the Leave side won by fifty-two per cent to forty-eight per cent, the pro-Europe forces had been making a vigorous effort to persuade the public that it made a disastrous mistake. That hasn’t happened. Under the leadership of the hapless Jeremy Corbyn, the Labour Party, the main opposition group in Parliament, has come around to toeing the pro-Brexit line. In advance of Wednesday’s vote, Corbyn ordered Labour M.P.s to support the Brexit bill, and most obeyed his edict—though fifty-two defied Corbyn and voted as their consciences dictated.
To be fair to the Labour Party, it is in a tough spot. Like U.S. Democratic congressmen and senators from districts and states that Donald Trump won, the Labour Party’s M.P.s can’t afford to ignore the views of their electors. Many represent working-class constituencies that voted for Brexit, and the rise of ukip represents a serious threat to them. Corbyn’s edict reflected a fear that if the Labour Party were seen as trying to overturn the result of the referendum, it could get wiped out in the next election. But for all this cold political logic, it was a sorry sight to see Labour, a party with a long tradition of internationalism and standing up for minorities, lining up alongside the Farages of the world.
Political self-interest also played a big role on the Conservative side, where loyalty to May and the Party leadership overcame the qualms about Brexit that many centrist Tories still have.