Possible Clues:

• Elector all at sea?
• Overlong fit at (anag) – one undecided about the election
• Water-borne constituent?
• Someone liable to change political allegiance between elections
• Giant revolt of unconventional political chameleon
• One who may be swayed either way at election time
• One without political affiliation
• Inconsistent type at the polls
• When crossing (at sea?), I could go to either side
• One undertaking crossing at sea?