The Senate, as of January 2021, is split 50/50 between the two parties, meaning VP Harris could be busy breaking ties...but that only happens IF there is a tie, which means every Senator votes in accordance with his/her party. In the case of Joe Manchin (D) of WV, this was not looking to be the case when the year began, and is even more clear now (SEP '21). He's one of the Senators to watch.