Is there any record of how many Jews actually supported the Nazi party before the Holocaust happened?

This is a difficult question to answer for any number of reasons, but I'll tackle it as best as I can. A major caveat before I get into what I can speak to.

How do we define who is Jewish? Do we use self-identification (i.e. people who think of themselves as Jews) or do we use the criteria the Nazis used themselves, because those two are not the same. There are many individuals who did not consider themselves to be Jewish who the Nazis considered to be Jewish. Victor Klemperer, who was a Protestant Christian with German Jewish parents (he converted to Protestantism in his early thirties) is an extremely well known example. To the modern reader, certainly to myself, I would consider Klemperer a Christian, as in my mind, Judaism is a religion, and religion is a fluid category that can change as easily as one's favorite color. The Nazis, on the other hand, considered Judaism to be a race. I won't get into the socially constructed nature of race, but suffice it to say that there is absolutely no concrete criteria for what makes a race, such that you'll find many scholars will even put the terms into "air/scare quotes" since the meaning of the term differs depending on who is using it. For the Nazis, race was a category that was determined mostly by blood. One's blood determined one's race, which was exhibited in the individual by other physical features (hair and eye color, or ones nose, for example).

Using self-identification, it is highly unlikely that there were very many, if any, Jews who supported Nazism. Hitler's antisemitism was well known long before he came to power. It was put on display for his followers at various public events, in his speeches, and in his book, Mein Kampf. The antisemitism of the wider Nazi movement was also never in question. They were an antisemitic party, through and through, and made no bones about it. An openly self-identifying Jewish person would not find much to like in a party that considered them to be a pestilence in the larger German body politic. Further, even if said Jewish person were a right-leaning authoritarian, there were other parties in the extremely fractured German right wing that were not as objectively antisemitic, although it should be noted that, as far as I know, German Jews tended to vote for the left leaning parties more than for the right wing parties.

Now, using the Nazi's criteria of racial Judaism, we come to a slightly different story. There were some individuals who supported Nazism who would have qualified as either Jewish or Mischlinge (mixed-race) by the Nazi's racial laws, the most famous of which were the so-called Nuremberg Laws of 1935. The major caveat here though is that they would not have considered themselves to be Jewish, and in some cases, might not even have known that they were Jewish under Nazi law until they bothered to look into their ancestry. German Jews were, by and large, very well integrated into the wider German population, and many were Jewish in name only (i.e. they did not attend synagogue or keep the law as a more observant Jewish person might). Germany is, after all, the home of Reform Judaism, one of the express purposes of which was to help Jews integrate more widely into the prevailing Christian culture. Because of this, there were some individuals who had Jewish ancestors who were completely unaware of their Jewish ancestry and who, for political reasons, supported Nazism. Emil Maurice, a close confidant of Hitler's at various points in his life and an early party and SS member was one such individual. He was a supporter of the regime, but his Jewish ancestry was discovered after he was required to prove his "blood purity" as an SS member in the 1930s. He eventually received a special dispensation from Hitler, being declared to have "German blood" (the laymen's term is an "honorary Aryan") and allowed to live. He served in the Luftwaffe in the war and survived until his eventual death in the 1970s. There were others, but they were, in every sense of the term, the exception to the rule. And I need to stress that these individuals did not consider themselves to be Jewish, regardless of what the racial laws said.

One final note is that this is something that is limited to Germany. Other fascist movements, such as the Italian Fascist Party, were not, at least originally, antisemitic, and very likely had Jewish supporters. I don't know a whole lot about Italian Fascism, but I know, for example, that in the Netherlands, the major fascist movement there, the National Socialist Movement (NSB), had a not insignificant number of Jewish supporters early in its run. It wasn't until later, that the NSB - which was originally aligned more towards Italian fascism than German Nazism, despite its name - came under the influence of the more German oriented voelkisch wing of the party that it started to openly espouse antisemitism.

If you have German and/or Dutch language skills, the two main books on these topics (that I've read, anyway) are: "Wer Jude ist, bestimme ich": "Ehrenarier" im Nationalsozialismus and Joodse NSB'ers: de vergeten geschiedenis van Villa Bouchina in Doetinchem