There are those who 'split' votes because of conviction of their views and a true desire to furnish an alternative for voters. There are those who are paid by the other side to run as they do to split votes to defeat an entire party. Both are facts of life and it is up to alert voters to figure out what's going on. On the eve of November Presidential election in 2000 I was at the Egan Center where all local media congregated, and many lead campaigners. As George W. Bush's victory clarified, the local Nader chapter staged a small march down the middle of the grand floor, to accolades which must have been mainly Republican. They might not have intended the Republicans to win, but they couldn't deny they had affected the way things turned out.
In Alaska, again, in 2012, we had a situation where an extreme RWing Republican, Joe Miller, won the primary, and the moderate Republican, and incumbant, Lisa Murkowski, had to run a full scale Senatorial campaign as a write-in. The only way she could win was for Democrats to combine with moderate/centrist Republicans to vote for her, thus in the particular case of the election the Democratic candidate was the vote splitter.