Ten percent is a lot for a third party.
I agree it would take a lot of money and a high profile candidate to achieve this level.
There would have to be a good reason for people to vote for a third party candidate. They would have to be the right candidate with a platform that appeals to people's dissatisfaction with the status quo.
In 1912, former President Theodore Roosevelt ran as the candidate of the Progressive Party and received about 27% of the vote, more popular votes and more electoral votes than the Republican, President William Howard Taft.
If there were similar circumstances as in 1912, this scenario would be possible, however, I do not expect to see this happen again.
There really isn't anyone with that much popular following in either party to pull something like that off.
I mean, McCain could try to pull something off in the event that both parties choose 'wingnuts,' but I doubt that his campaign would get much of anywhere.
The only person with enough pull to do that is Bill Clinton...and he's ineligible to run again.