There's something ominous going on in England. The Labour Party is purging members it thinks will vote for Jeremy Corbyn as party chairman. Corbyn, a member of parliament, and his supporters want to return the party to its working class roots and away from the Neoliberalism of Tony Blair and subsequent party leaders.
article by Kerry-anne Mendoza published in the New Internationalist titled The Labour Purge Is Underway, in which she reproduces an email sent around by the Labour Party leadership that I've posted here.
Blair is often compared to Bill Clinton, who led a movement of conservative Democrats-- see Democratic Leadership Council -- that included people like Al Gore, Joe Biden and Tony Coelho who took over the Democratic Party in the 1980s and 90s and moved it to the right. Both Blair and Clinton as prime minister and president were able to pass things like NAFTA and legislation dismantling social services that no Republican president or Conservative prime minister could have gotten away with at the time. The Democratic and Labour parties today unashamedly promote Reaganomics economic policies and remain "liberal" on only two social policies, gay marriage and abortion, and posture on things like the environment and racial equality only as needed to prevent a revolt of their base.
Party orthodoxy is enforced in various ways. In the US it's usually thought that the election process is the primary way; vast amounts of money must be raised and since rich people have the money, rich people call the tune. But it's hard to even get on the ballot in the first place unless you have the approval of the party establishment. In New Mexico, for example, both parties hold nominating conventions where a candidate has to receive a certain percentage of votes from enrolled party members to get a spot on their party's primary ballot.
I've wondered if it would be possible to take over a mainstream political party by getting a lot of like minded people to join the party. We're seeing what happens when you try that in England.