This is a reasonable question that cannot be answered merely by dictionary work. I do not repeat all the definitions here but if we look for example in the Cambridge Dictionary online we get
Thereby = as a result of this (failure to investigate)
Effectively = in a way that is successful and achieves what you want
Or effectively = used when you describe what the real result of a situation is:
Allowed = Permitted or similar meaning. Other meanings are also given.
To stand = there are too many meanings of stand for me to list. One that is relevant here is :
Stand = to be in a particular state or situation
To understand such English from dictionary work therefore requires the reader to choose from too many possible combinations of these definitions to reach a reliable conclusion. Even some less literate native speakers would have difficulty in comprehending the combination of the four elements.
If the irregularities are not investigated and are permitted to be uncorrected until Inauguration Day, they will remain as precedents and examples that corrupt future election processes.