Illinois held its 2010 primary on February 2. Although the State Board of Elections hasn’t released the official election returns yet, Green Party activists have collected data from the various counties and have calculated that over 5,501 voters chose a Green Party primary ballot. See the county-by-county breakdown here.
In 2008, the only other year the Green Party had a statewide primary, 3,014 Illinois voters chose a Green Party primary ballot. Before that, no party other than the two major parties had held a statewide primary since 1990 and 1988, when the Illinois Solidarity Party held one. In 1990, only 418 voters had chosen an Illinois Solidarity Party primary ballot, and in 1988, only 525 voters had chosen one.
Before that, there hadn’t been a statewide primary for a party other than the Democratic and Republican Parties since 1926, when the Progressive Party had one.