Probably thousands of political and religious leaders--there's no way to know for sure.

Fidelity to the Biblical description seems to matter less here (a figure declaring himself to be God in the temple, etc.) than the expediency of using the concept/term to refer to figures that Christians think are the "embodiment" of evil. (I suppose any figure that becomes revered/idolized might be a candidate for having "exalted himself" or whatever.)

The anti-Christ is often conflated with the beast "whose number is 666." This almost certainly originally referred to Nero Caesar, but has also been applied to a plethora of figures throughout history. Again, although this originally hinted at the numerical value of the letters in someone's name (which would seem limiting), people have still managed to interpret dozens, hundreds of people to fit this (I recently read a pretty telling monograph on the issue: The Contribution of British Writers between 1560 and 1830 to the interpretation of Revelation 13.16-18 [The Number of the Beast]).

As I see another commentator has already noted, an exact account of how many people have been identified as the Antichrist would be all but impossible, given that biblical interpretations vary a great deal and any number of small sects have come and gone in the past millennium.

In terms of the use of "Antichrist" that you seem to be indicating here, that is to say an eschatological figure who will play a role in the apocalypse (and as such closely associated with the Beast of Revelation, the number 666, etc.), the common image has changed considerably over time. One of the most common medieval depiction of the Antichrist was something akin to an inverted hagiography: a Christ-like figure, often Jewish, performing miracles and declaring himself as God in the temple. A good example of this sort of narrative was the Play of Antichrist from the 12th century. But, this is a sort of Antichrist that was not identified as some particular contemporary individual, and for the most part the Roman Catholic Church was content to leave the Antichrist as a figure in the periphery of history.

This basic dynamic changed during the later middle ages with certain groups within the church speculating that the Antichrist would be, not an outsider, but a figure within Christendom. The Papal Antichrist was a concept that began to gain some currency, which fit the general narrative of an Antichrist who would set himself up as God in the temple (or Vicar of Christ, as the case may be). Conversely, given the conflict within Christendom between the Papacy and the Emperor Frederick Barbarossa in the 13th century, Pope Gregory IX went so far as to call Frederick the Antichrist. These are broad strokes, but for more on the medieval Antichrist I recommend the works on the topic by Bernard McGinn and Richard K Emerson.

The real change came with the Reformation, wherein the major conflict within Christianity brought about some real and immediate eschatological expectations. As a rule, most of the Protestant Reformers came over the course of the 16th century to regard the Papacy itself, as an institution, to embody the Antichrist, more so than an individual pope. The image was quite common and fit into the complex historical and apocalyptic narrative of various Protestant churches, which saw the Church of Rome as a persecuting and Antichristian church that has suppressed true Christianity, which was due to fall imminently. Broad strokes, once again, but this opposition set the basic dynamic around the Antichrist for a century or two. Good examples of this kind of narrative would be John Foxe's Acts and Monuments (or the Book of Martyrs), or in the "Christ and Antichrist" series of engravings by Lucas Cranach the Elder, with commentary by Philip Melanchthon, which contrasted the life and ministry of Christ with that of the Pope.

More variously, some Reformation interpretations included seeing "the Turk", that is to say the Muslims of the Ottoman Empire, as the Antichrist which would ravage much of the earth's population. Conflicts within English Protestantism during the Civil Wars and Revolution of the mid-17th century saw some sects like the Fifth Monarchists associating Charles I and the institution of monarchy itself with the Antichrist, and tarring Oliver Cromwell with an antichristian brush as the "Little Horn" of the book of Daniel. Once again, exact identification as "Antichrist" as such were sometimes less common than general association with the apocalyptic figure.

At the same time, Antichrist could also be associated with more general sins and vices, as with "the Flesh" and worldly things in the works of Gerard Winstanley or the Quaker George Fox.

By and large these general characteristics in interpretation continued, and you still don't need to look to far to find some churches that continue to associate the Pope with the Antichrist. For a particularly thorough example of interpretation, Ian Paisley of the Free Presbyterian Church has spent a lot of time since the 1960s branding as Antichristian not only the Pope (see youtube for a clip of him denouncing John Paul II in the European parliament), but the European Union and any form of internationalism.

You can't really go too far without coming across more general fears associated with the Apocalypse and Antichrist. Individual bar codes and ID are one thing that gets trotted out as a possible "mark of the beast". What's more, the specific role of Antichrist as individual is something that can get attached to anyone who is elevated or revered for whatever reason. President Obama is one person who's attracted this sort of attention more recently, but he's hardly the first politician to find himself labelled in this manner. The "Left Behind" series of books is a pretty good example in contemporary Evangelical literature that gives a sense of what a charismatic politician Antichrist looks like in the eyes of some of these groups.

Gregory of Tours shares a charming anecdote of a sixth-century French peasant who, after having a spiritual experience, came to think that he was Jesus Christ.

Gregory mentions his alleged powers of prophecy and faith healing. While he attributes these powers to Satanic tricks, he says that several bishops and thousands of laypeople followed this man. Gregory believed he was an anti-Christ.

Ultimately, this unnamed man was killed by Frankish warriors, who tortured his accomplice, a woman calling herself Mary.