Zeal of the convert
The zeal of the convert is a phrase describing the typically fierce devotion of someone whose belief system has changed because of personal experience or argument, especially as compared to someone who has held their beliefs since childhood. In addition to some empirical support of the phenomenon, the occasionally excessive fervency of converts has long been proverbial.
- Paul of Tarsus, a Pharisee who persecuted Christians, would go on to be one of the most devout and pivotal figures among the early Christians.
- Martin Luther, a liberal Catholic who denounces violence towards Jews as counter to God's plan, would later be radicalised by his anti-semitic students and ends up inspiring the Nazi's policies with his book On the Jews and Their Lies.
- The New Atheists consist of a group of several outspoken and aggressive atheists, many of whom were converted from Christianity to their solid disbelief.
- Ultraconservative American radio host Michael Savage was once a liberal consort of hippies, only to later become one of the angriest of all the media's opponents of liberalism.
- Salem Radio hosts Michael Medved and Dennis Prager both claim to be former liberals prior to taking a hard-right, anti-liberal turn.
- Professor Ronald Radosh went from being a radical Marxist (arguably pro-Maoist even) to an ardent neoconservative. Similarly former Trotskyist leader James Burnham eventually become regarded as the original neoconservative, and many former Communists such as David Horowitz have taken similar shifts in their positions (from far-left to strict neocon).
- Many former British socialists such as Melanie Phillips and Peter Hitchens would later become nationalistic wingnuts.
- Benito Mussolini going from a Democratic Socialist to an anti-socialist fascist.
- Thomas Sowell going from being a Marxist sympathizer to a very right-wing libertarian.
The political conversions in recent years, especially from "liberal to wingnut", are a little dubious at times, with some cynical liberals and moderate conservatives (such as Mike Lofgren) pointing out that the concept of "redemption" has become a big feature among the religious right, so claiming to be a liberal who have "opened their eyes" and seen the "truth" can be a good way to get sympathy from their target audience. That being said the "conversion" is oftentimes genuine, and in recent years has tended towards a hard-lefty going to the hard-right, perhaps because the fall of Communism and rise of reactionary politics in the western world gave a more appealing "black-and-white" political philosophy tending toward the political right.
 See also
- Pew Research Forum survey on the different levels of devotion between converts and childhood believers, by religion.
- A blog post from the reactionary right-wing American Thinker where a crazed author explains how they went from being an extreme liberal to an extreme conservative