Why are there so many whiny wimps crying about a contested primary? I wasn't alive in 1980, but from what I know, it was a bitter fight between Reagan and Bush and probably a few others. And we came out better for it.
Yes -- stifling the opposition in the primary weakens your bench, and so far as I can figure, standing VP's don't have that great of a track record:
2000: Gore (won nomination, lost election)
1988: Bush (won election)
1968: Humphrey (won nomination, lost election)
1960: Nixon (won nomination, lost election)
1952: Barkley (lost nomination)
1940: Garner (lost nomination, challenged Roosevelt)
1896: Stevenson (lost nomination)
1856: Breckinridge (lost nomination, ran as Southern Dem)
1836: Van Buren (won)
1800: Jefferson (won, challenged Adams)
1796: Adams (won)
Yeah, there are some special cases in there, and the system is different now than it was years ago. But the fact remains that standing VP's often lose, too...