Whatever happened to the Jimmy Stewart-style filibuster?

Here is a news story titled Whatever happened to the Jimmy Stewart-style filibuster by Aaron Erlich

Since the 1960s the "two-track" system devised by Mansfield has prevailed, preventing old-fashioned filibusters. As John W. Dean, President Richard Nixon's former White House counsel, has written: "On the one hand, the two-track system strengthened the ability of the majority to withstand a filibuster by enabling it to conduct other business. On the other hand, it made it easier for the filibustering minority, which did not have to constantly hold the floor."