When Barack Obama declared in 2004 that there was no Red America or Blue America, it was states like Virginia that he probably had in mind. In recent years, Virginia has been fertile ground for candidates of both parties: The state’s current governor is Republican, but its previous one was a Democrat; in 2008 the state voted for Barack Obama, but four years earlier it went for George W. Bush. State-wide elections in Virginia have traditionally been hard-fought, and they’ve featured their share of ideologically-blinkered candidates (see: former governor and current Senate candidate George “macaca” Allen), but they’ve also generally lacked the vitriol and coarse ideological rhetoric of the country’s most polarized states.

The people of Virginia may have justly earned a reputation for keeping an open mind at the polls, but the electorate is not the only reason that the state has historically been such a bastion of political diversity and pragmatism. One important factor is the state’s open primary system, in which voters do not have to be a member of a party to vote in party elections. But if a group of Republican state legislators currently pushing to close the state’s primaries has its way, Virginia’s reputation for political comity—and its days as one of the country’s quintessential swing states—may soon be done for.

Virginia is one of 17 states across the country to have such an open or semi-closed system. Geoffery Skelley, a political analyst at the University of Virginia Center for Politics, tells me that the effect of open primaries, especially in competitive races, has been to strengthen the state’s political independents and dilute the influence of partisan ideologues. It’s no accident that states with open primaries often nominate more temperate politicians than those with closed primaries.

In Virginia, the open primary system has its roots in the state’s one-party past: The state was once so dominated by Democrats—Republicans were hardly a presence in the state at all until the 1960s—that their primaries essentially served double-duty as general elections. Open primaries were intended to encourage participation, and to broaden the party’s appeal so it was more reflective of the state’s diversity.

That may be precisely why Republicans want to get rid of the open primary. After their surge of recent years—they currently hold the Governor’s mansion, as well as the state House and Senate for only the second time since the Civil War—Virginia’s Republicans seem to be seeking to consolidate their ideological grip on the state. To that end, they have decided to target the open primary system itself, seemingly in a bid to heighten their differences with their competitors and to ensure that the party puts forward more consistently conservative candidates—even at the expense of perhaps polarizing the state irrevocably.