To become an antipope one has to split the College of Cardinals down the middle. In the earliest days of the papacy, the College did not exist so a popular candidate for pope would just have to make a ruckus and have the populace elect him. If that didn't work, get the Byzantine Emperor—technically the secular head of the church at the time—to elect him. Felix II, Laurentius, and John XVI were all antipopes elected by Byzantine Emperors. Antipopes who claimed popular election, though, were often guilty of election fraud.
They also sometimes were guilty of nothing other than being the victims of court intrigue. Many early antipopes were popularly elected by either died before being able to do anything or were undermined by a local secular power. In the former case, the successor would brand his predecessor an antipope, thereby strengthening his own position. In the latter, the secular power may or may not have motives in denying the pope power, but without it, the pope becomes nothing and the clergy or College choose another.
Once the College of Cardinals was formed, things should have become simpler. The College convenes and votes until a single candidate wins. Majority rules! But sometimes the College is divided or members are not able to attend and another candidate gets an equal or strong second to the winner. In these cases, that second candidate may choose to forego the status quo and seek the papacy regardless of canon law. Support by a strong patron, such as the Holy Roman Emperor, may also lead a strong papal contender to challenge the incumbent. Whereas in monarchies, it is generally a pretender or usurper who attempts to claim another's title, with the papacy it is generally one who had strong support buy failed in the last round of voting.
With the Holy Roman Empire, a similar situation arose. Squabbles between imperial candidates was common but the College of Electors generally had the final say. Being only seven members, it was hard to not have a majority. But it was not unheard of. Like the papacy, electors could be absent or abstain their vote, thereby leading to ties and challenges. Papal support often encouraged imperial candidates to seek the throne, violently if necessary. This could result in antikings. They are antikings because the Holy Roman Emperor does not gain that title until he is crowned by the pope (or, in later days, acknowledged by the pope). Prior to that coronation, they are simply the King of Germany.
The Investiture Controversy
I will not go into details of the crisis, but in summary, the role of the Holy Roman Emperor over clerical appointments (investitures) was in question and the Empire and the Papacy were butting heads. In 1075, Pope Gregory VII issued a statement saying that only the papacy could appoint bishops and only the pope had the power to depose monarchs. Emperor Henry IV responded by denouncing Gregory VII. Gregory countered by excommunicating Henry and deposing him as King of Germany. In 1077, Rudolf, duke of Swabia, was elected by a group of German nobles to replace Henry.
|Emperor Henry IV requesting mediation.|
|Antipope Clement III (center) with Henry IV (left)|
The papacy continued to struggle against Imperial-supported antipopes until 1122. Sylvester IV and Gregory VIII were supported by Emperor Henry V, the son of Henry IV. Both were deposed by the legitimate popes and placed in monasteries after all their followers had dissolved. In 1122 the Investiture Controversy was finally put to rest.
The Hohenstaufen Plight
A brief schism occurred in the late 12th century soon after the rise of the House of Hohenstaufen to the Imperial throne. The issue was over supremacy: was the pope superior to the emperor, or vice versa? What resulted was a whole slew of antipopes. Victor IV was the first of these popes, followed by Paschal III and Callixtus III. None of them did much in the way of papal work and were seen largely as Imperial pawns. Emperor Frederick Barbarossa finally came to terms with the legitimate pope, Alexander III, and most was forgotten for the time being. Interestingly, though, the Imperial antipapacy continued with Antipope Innocent III, a feeble man who was soon arrested and incarcerated for the rest of his life by the true pope. For 150 years, the papacy finally had peace in its succession.
|Holy Roman Emperor Frederick II Hohenstaufen|
|Antiking William of Holland|
The Unexpected Interregnum
The centuries of fighting since the fall of the Carolingians in 911 had caused the only real interregnum in the empire's history. Conrad IV died in 1254. Conrad V was young and never was recognized as Holy Roman Emperor or even King of Germany despite his numbering. For two years, from 1254 to 1256, William, count of Holland, was the only Holy Roman Emperor in Germany, though most did not recognize his legitimacy.
|Antiking Alfonso of Castile|
The Pope's Last Infight
The Papacy was not so lucky. The Western Schism developed in 1378 over the election of a successor to Pope Gregory XI. The French and Italian groups within the College of Cardinals had grown to dangerous levels. When Gregory died, the Roman populace demanded a Roman pope. Thus Urban VI, not Roman but still Italian, was elected. The French cardinals rebelled and elected Clement VII. Since he was in opposition to the majority, Clement VII had to flee and settled at the papal estates in Avignon, France. When Urban died, instead of electing the already-chosen Avignon pope, the remaining cardinals elected Boniface IX. Meanwhile, the successor of Clement was Benedict XIII. Boniface died and Innocent VII and then Gregory XII succeeded him.
|The Western Schism divided the Catholic world|
At this time, in 1409 the Council of Pisa was called which sought to reunify the papacy. Instead, the leader of the movement was elected Pope Alexander V, a role he hoped would bring unity to the papacy. Instead, it just added a third claimant to the papal seat. Alexander died within the year and John XXIII was chosen as his successor. The Pisan popes are considered antipopes but retain some legitimacy within Catholic circles, as opposed to the Avignon popes which are universally regarded now as antipopes. In any case, Pope Gregory XII and Antipope Benedict XIII agreed to renounce their claims to the papacy in favor of a shared successor. Gregory lived on for two years, during which time no successor was named and no pope sat on the papal throne. In 1417, Gregory finally died and Martin V was elected to succeed him. The Pisan Pope John XXIII renounced his titles. The Avignon Pope Benedict XIII, however, did not. While the Western Schism was officially over and the Catholic Church was united again, a small splinter group of the Avignon papacy lived on for a few years yet
|Pope Martin V|
The history of the papacy and the Holy Roman Empire is rife with examples of pretension and intrigue, but the role of the antipope and antiking to history is fairly unique to elective monarchies. Where in most countries there is little doubt to the legal successor, in elective monarchies things can be doubted, ballots can be forged, and strings can be pulled. For three centuries, the Catholic Empire in Central Europe was being continuously shaken by these intrigues and that led to the decline en masse of Catholic control over Europe. In other words, Martin Luther was only making obvious what four hundred years of history had already pointed out.