In the past, Lloyd Bentsen has won his elections by close to sixty percent of the vote, so I say that he survives in 1994 and 2000. This creates an alternate timeline in which Ted Cruz never gets to be a senator.
They were when Dem incumbents in the south still routinely performed strongly and before realignment as well. In TN for example Senator Sasser for example won over 60% in 1982 and 1988 but then in 1994 was defeated by 14 points.
in 1994 I think Bentsen still survives due to TX Republicans not having established their dominance, but in 2000 with Bush on the top of the ballot and TX Democrats infrastructure having been utterly decimated in 1996 and 1998, I dont think Bentsen can win.
If McCain was the nominee, Bentsen could probably hang on just barely, but not with Bush being the nominee