There is such evidence. The U.K. provides some interesting examples on that point.
You may remember that in the early eighties a new party, the SDP, arose in Britain. It was basically Labour Party members on the right and Liberal Party members who thought that they could rewrite the electoral map in Britain by joining this new party.
In the first election, Labour and the SDP split the vote on the left, and the Conservative Party, which had only about 40% of the popular vote, got a huge majority in Parliament. In the next general election the SDP decided to not even send candidates to certain electoral constituencies precisely because they were worried that the same thing would happen again.
There have been many examples in Britain.