Poll: There was nothing that could prevent them ____ it again.
- Votes: 470
- Comments: 2
- Added: September 2004
- Polls: 1,170
- Votes: 690,276
- Comments: 4,855
Prepositions are more commonly attached to verbs in US English, but it adds no value here, so in UK English should be excised.
Dictionaries make no distinction between the two forms (with/without the preposition), and both are equally common in BrE and AmE.