The future Charles V was a member of the House of Habsburg, so he obviously had extensive connections and influence within the empire even though grew up in the Low Countries before becoming King of Spain. But his background still seems a little odd to me for a Holy Roman Emperor. I wonder if the unusual aspects of his candidacy made Henry VIII of England and Francis I of France seem like more plausible candidates than they would have if, say, Charles V's cousin and eventual successor Ferdinand I had been the Habsburg candidate.
Modern infotainment "news" anchors would have had an absolute blast reporting the 1519 imperial election.
For centuries, the most important factor in imperial elections had been money, no question. In the 13th century, outright bribery led to the split election of outright foreigners Richard of Cornwall and Alfonso of Castile as King of the Romans. The exercise proved futile for both: only Richard was ever crowned, and Alfonso never even set foot in Germany. Money continued to change hands in imperial elections. Charles IV was so annoyed at the large bribe he had to pay that he outlawed "electoral pacts" in 1356...only to utilize them to see his son elected. The loophole, looking at other votes, seems to have lain in
The interesting thing is that in the messy 15th century of successful political and unsuccessful Church reform, money slipped out of favor as the grease of elections. Frederick spent a little money and made a couple promises to get Maximilian elected king of the Romans and therefore imperial heir, but nothing like the enormous sums of earlier centuries.
For the 1519 election, outgoing (but alive) emperor Maximilian I was on record that his grandson Charles, whom did he not know well and did not like, not become emperor. He had sworn in a treaty to make Louis of Hungary his heir while informing the imperial electors that he wanted Henry of England. Meanwhile, by 1516 Francis of France was amassing support among electors by promising bribes (pensions, lands, marriage alliances) in an amount that deeply worried supporters of the other candidates.
In 1517, the Habsburgs changed the game by announcing (a) Charles' candidacy (b) Maximilian's support for him.
Maximilian wanted Charles crowned King of the Romans/imperial heir while he was still alive. He borrowed enormous sums of money, mostly from the ridiculously rich Jakob Fugger, towards bribing electors away from support for Francis in particular. But he ran into a roadblock: the most pro-French candidates (for political reasons or political-bribe reasons, i.e. the lands they stood to gain) argued that it was not possible to crown Charles as king of the Romans because that was Maximilian's title on a technicality--he'd never formally been crowned Emperor.
Then Maximilian changed the game again by dying.
At this point, the qualities of the candidates came to the forefront, and "qualities of candidates" meant something very different in 1519 than they might have earlier due to the European geopolitical situation. The emperor's stated support for Charles combined with the financial stakes or requirements had caused Henry to slide quietly out of the main competition, leaving Francis and Charles in a face-off (with, as we will see, simmering support for Frederick of Saxony as a "next best" candidate).
Spain rather than France was the major martial threat to papal power in Italy, leading the pope to favor a French-German alliance rather than uniting the power of Spain to the Empire. One elector held his position thanks entirely to the nobles of Bohemia, meaning his vote was their vote, and they were firmly in the Habsburg camp. And perhaps most importantly, the external threat to the empire came from the east. The propaganda for Francis stresses his moral character; the propaganda for Charles, the massive quantity of his German armies located in Germany and aren't these armies German and in Germany?
Historians make much of Saxony elector Frederick the Wise's support for Charles, because Frederick would go on to shelter Martin Luther after the Diet of Worms and Charles had to grumble and look the other way. Frederick, in fact, was not really inclined to favor the Habsburgs. Dismissed from the emperor's service in 1498, he was still owed a back salary of, well, more than Maximilian had paid to obtain the throne in the first place.
But as Henry Cohn argues, Frederick was even more grouchy with Francis. Specifically, with the deals he knew Francis had made in order to secure support for his position.
So competition between Charles and Francis came down to a lot of things: money, heritage, geopolitics, personalities, intelligence/espionage, and military strength. But there is one interesting phenomenon in the sources leading up to the collection. More and more stress was placed by propaganda and in letters among advisers on the need for a German ruler. It seems that the less-than-Austrian backgrounds of both candidates indeed provoked concern as the reality that the candidate would rule immediately, not just be the current emperor's heir for that time down the road, set in.
One interesting theory that resulted from this (already in the sixteenth century, though not by anyone in direct attendance) is that Frederick was actually elected emperor but refused the throne. There is a gap, a declared delay in the election during the June meeting. Henry Cohn has argued that the erstwhile supporters of Francis sensed they had lost the battle and threw themselves into a last-ditch efforts to elect someone besides Charles. (Remember, Frederick was no friend to the Habsburg monarchy and his problem with the non-Habsburgs was specifically Francis). But Frederick was on record as preferring to work behind the scenes, with more than one scholar over the centuries archly suggesting the source of or support for his moniker "the Wise."
Cohn's great article on the election is titled "Did Bribes Induce the German Electors to Choose Charles V as Emperor in 1519?" He is writing against a vast historiography that basically sees Maximilian spending nearly 900,000 gulden to get his son seated on the throne. As Cohn shows, the answer is not yes or no, but "yes and also."
A great, readable, and above all English source on imperial and ecclesiastical politics in this era is Thomas Brady, German Histories in the Age of Reformations.
What made someone a viable candidate to be Holy Roman Emperor? Were there specific criteria or was it more a matter of power and influence? Why were the Kings of kingdoms which were not in the Empire viable as candidates for Emperor?
Is there any reason to assume Charles V didn't already speak German?
Also, to what extent was the Holy Roman Empire German-speaking ? Was German a lingua franca? What language was used by nobility ? Seeing as there are extensive dialectical differences in Germany with what is spoken by the "people" often differing quite a bit from standard German, can we even assume that there was something that was well enough defined to be considered German by those inhabiting the HRE ?