You don't think this is happening already, regardless of UK / rUK? Neither the Cons or Lab can fight their way out of wet, torn, paper bag, and the Lib Dems have never been as irrelevant. Hell, DC couldn't get a majority over Gordon Brown in a recession. I am utterly unsurprised votes are bleeding away at a local level to fringe parties, and I fully expect that to carry over to a hung parliament next year.
The democratic process at work. When people turn to UKIP / BNP et al you can be sure your major party message is falling on angry, not deaf, ears. Sow it then reap it etc.
Harrumph.