Grassley is “pro temporare” of the Senate if Pence is unable to take electors on the 6th
https://en.m.wikipedia.org/wiki/President_pro_tempore_of_the_United_States_Senate
The president pro tempore of the United States Senate (often shortened to president pro tem) is the second-highest-ranking official of the United States Senate. Article One, Section Three of the United States Constitution provides that the vice president of the United States is the president of the Senate (despite not being a senator), and mandates that the Senate must choose a president pro tempore to act in the vice president's absence. Unlike the vice president, the president pro tempore is an elected member of the Senate, able to speak or vote on any issue.