In the 33 regularly-scheduled U.S. Senate elections held last month, the total for all Democrats was 50,770,269; for Republicans, 32,803,554.
These totals do not include votes cast for minor parties that cross-endorsed a major party nominee. Nor do they include the votes for independent U.S. Senators Bernie Sanders and Angus King, even though some sources tend to lump their vote totals into the Democratic column, since those two Senators support the Democratic Party when the Senate elects its leadership.
The main reason the Democratic margin is so huge is that in California, no one was permitted to vote for anyone for U.S. Senate except a Democrat. So the Democrats piled up 11,113,364 votes for U.S. Senate in California, with zero votes for anyone else.