The filibuster is not in the constitution. It is part of senate rules wasn’t in place for a lot of years. Can be changed anytime
Simce only 2003.
And, a bit of history:
Filibuster first limited in 1917 with 66 votes...by Democrats
Filibuster further limited in 1975 with 60 votes...by Democrats.
Filibuster further limited (for convenient votes) in 2013 with 51 votes...by Democrats.
According to Rush this p.m., it was passed by the Democraps in 2003 to prevent confirmation of Estrada, a “W” appointee. It had been used until it failed to meet the needs of Democraps at which point Harry Reed and the Senate nuked it to pack the lower courts with Leftists.