The Democrats are strong enough to marginalize the Green Party's role in state government, but not strong enough to get rid of them. He goes on to say that they will both get tired of seeing conservative Republicans get elected, so they will merge. Second, it will ease the angst of voters who would like to vote for the person or party they really believe in but who vote instead for someone they feel they can at least stomach in order to defeat the one they can't. Third, this voting change will also overcome the downside of plurality voting, in which, when three or more candidates are vying for the same office, the winner gets less than a majority. This of course is happening more and more in state-wide elections.
Third parties offer candidates regularly.
Their electoral capability grows stronger, given, among other factors, the clean election law which offers public financing to people and parties who hitherto have not had access to big bucks normally given only to the Democratic and Republican candidates. The voting change I am pointing to is called IRV, Instant Run-off Voting. It works this way. Voters at the polls rank candidates in order of preference rather than just one vote per person. Voters usually have the option to rank as many or as few candidates as they want.