According to Der Spiegel 52% of Austrians were against an independent Austria and in favor of unification with Germany
in 1965.
http://www.spiegel.de/spiegel/print/d-13531257.html
Tirol and Salzburg both had votes in 1921 to join Germany which passed both by a 98+ % in favor. It was blocked by the Entente powers which threatened to invade in case they tried to join Germany.
And it should be remembered that the first Unification attempts after WWI were started by the Austrian socialists. Austro-German unification had support through all parties and classes of society.
To be fair, 1918-1922-ish was a very awkward time in Austria, which was still reeling from a traunatizing defeat-and-dismemberment. While Tyrol did vote for union with Germany, they also voted for union with Switzerland within that timeframe. Take that as you will, but IMO it was a sign of confusing time and massive difficulty filling the vaccuum left by the collapse of the Imperial-Royal government (ironically, the Reichsrat continued operating well into 1919 despite the existence of German-Austria) and the very important issue of Austrian national identity which had completely disappeared with the Empire. Plus, I would take in consideration the results of the elections right after Saint-Germain-en-Laye, when the nominally anti-Anschluss Christian Socialists narrowly won. Anschluss obviously had popular support, but it certainly wasn't as garanteed as people sometimes claimed.
Anyways, that's not
entirely on-topic. By 1938, the situation was just as unclear: the Social Democrats, whom had been chased out of power during the Civil War, still mostly supported union with Germany, but heavilly opposed thr Nazis and they, along with the Communists and Monarchists (both were anti-Anschluss) formed the backbone of the resistance in Austria. Which brings me to question this:
FWIW, the 1957 Encyclopedia Britannica (article "Austria", p. 748) states "It would be an error to dismiss this vote as meaningless or forced. Though many Austrians were not yet nazis. they welcomed the Anschluss almost unanimously. Even the Socialist Karl Renner, then living in retirement, did so."
I seriously doubt this statement. From what I read, he saw the Nazis as just as bad as the Austrofascists and that they wouldn't last (i.e. he massively underestimated them). He supported union with a
democratic Germany, not the Nazi invasion.
It's clear that Austria had a big share of very loyal and committed Nazis, but it's definitely not clear how the majority of Austrians felt; especially with how the Fatherland Front ruled pre-Anschluss Austria with no significant issue until thr Nazis began seriously pressuring them. IMO, it's more fair to say that the vast majority of Austrians were apathetic towards Anschluss and the Nazis. Thus, the Nazis were easily able to win over the majority of right-leaning Austrians and silencing the rest.
I might also add that once German troops had crossed the border and Schuschnigg was bullied out of office, there was no chance of armed resistance; it was far too late. Had the planned plebicite been held without the Nazis interfering, it seriously could have gone either way.