Commentary for Avodah Zarah 97:4

Eliezer and the rabbis disagree over a case where two pieces of leaven (starter dough) fall into a batch of dough and cause the dough to rise (neither was sufficient in and of itself). One of these pieces is terumah and can be eaten only by priests, and one is non-sacred and can be eaten by anyone. According to R. Eliezer, the status of the dough follows whatever the last piece of leaven was, because this is the leaven that causes fermentation. Abaye adds that if the forbidden leaven was left in there, then in all cases the dough is prohibited. Thus R. Eliezer seems to hold that in cases with two causes, one permitted and one prohibited, the result is prohibited. The rabbis would be lenient. This seems to locate the dispute between the two baraitot in yesterday’s section.