At
this website, dated 10/13, an average of the many, widely varying, polls gives this result:
Romney 22.7
Cain 20.3
Perry 13.7
Gingrich 8.3
Paul 8.2
Bachman 4.8
Santorum 2.0
Huntsman 1.6
This amounts to 81.6%. Hence, I would put the undecided at 18.4%
Were these trends to continue into the convention, the two frontrunners would be Romney and Cain, neither of whom would have enough votes to come near clinching the nomination. This would give Perry, Gingrich and Paul incredible leverage over anyone who might court their delegates. Were Perry to throw his votes to Cain, and Gingrich were to support Romney, the frontrunner standings would be:
Cain 34%
Romney 31%
If Paul, Bachman and Santorum give their cumulative 15% to Cain, and Huntsman backs Romney, the standings would be:
Cain 49%
Romney 32.6%
So, is it all over for Romney? Not neccesarily. If the undecided 18.4% vote for Romney the standings would be:
Romney 51%
Cain 49 %
Though Romney would officially win, the Republican party would be effectively fractured. If Romney and Cain split the undecided vote at 9.2 each, we would have the following standings:
Cain 58.1 rounded to 58%
Romney 41.8 rounded to 42%
Cain here is the definite winner, but Romney's supporters would still be able to split the Republican Party.
Of course, all this is speculation, and the trends
won't remain the same, meaning that everything is fluid and meaningless at this time.