In a continental Europe-style multiparty system, it would probably be possible for some 5% or 10% minority party to position against the current government and rise to above 30% in about a decade, thus rising to power. For example Fidesz in Hungary grew from 7% in 1994 to 53% in 2010 ( http://en.wikipedia.org/wiki/Fidesz ).
In the more stable US two-party system, you may need to resort to somewhat older methods, which are still widely used around the world even in present days: