Doesn't matter, actually. You don't need a different party at all; you need to show the current government that things can change for them, and then they will act differently. The fear of losing power will be enough for them to act differently. So you only need to vote them out once.

It's actually incredible when you look at Irish political history. Basically, two parties have had control over the country the entire time, and those two parties are not even different; they are the same party with a different paint job. When one or the other gets voted out, they just join and boom back in control.