The "progressives" who have come out in support of IRV are a very small minority within their own party.
The way to pass IRV is to run Greens aggressively for public office right now, under existing electoral law, rather than to postpone serious campaigns until the glorious day when we have the ideal, "spoiler-free" system that Cobb envisions.
With IRV, if no candidate reaches the threshold, the candidate with the least number of votes is eliminated and her/his ballots are redistributed according to the voters' second choices.
Under IRV, the process is just as simple as for single seat elections for the voters who still specify their choices according to first, second, third, and so on.
The answer, simply put, is the difference between enacting 1 or 2 IRV laws by the 2004 Presidential election and enacting 10 to 15.
Now, as difficult as it was for the GPMI to collect and submit the required 32,000 signatures for ballot status, it would be impossible for us on our own to collect the over 242,000 signatures that would be required to place an IRV initiative question on the ballot in Michigan.