He's going to lose if he's forced into a runoff, and judging from those "time for someone new" numbers, he will be.
No, he's probably not -- in SC, runoffs occur almost immediately after the general election, so usually the key opposition figure that emerges fails to unify the vote and the most prominent candidate wins -- this is how Mark Sanford won, and he was far worse than Graham. The only counterexample I can think of is the Senate primary in 2004 (where DeMint emerged as the key opposition figure, then beat ex-Governor Beasley), but Beasley was far weaker than Graham or Sanford (Beasley led DeMint by just 11 points in the first round; Sanford led his opponent Bostic by 24 points, and in this poll Graham leads Bright by 29).
The danger to Graham is if someone -- probably Bright -- surges. But I don't think that's too likely considering no outside groups seem interested and he has far less money than Bright and other contenders on his heels to contend with.