I swear I never heard this expression "So, the state of xxx is still very much in play" 4 years ago.
How the quotes are used throughout the following article (they are not sarcastic/ironic quotes) also suggests that this use is new.
Arizona acts not like state 'in play'
Robert Robb
The Arizona Republic
Nov. 9, 2004 09:32 AM
Postscript thoughts about the Arizona election:
• Tell me again the one about Arizona being "in play" in the presidential race.
In 2000, George W. Bush took the state by the registration margin Republicans then had over Democrats, about 5 percent. advertisement
In 2004, although both parties had lost registration share to independents, Republicans still maintained about a 5 percent advantage over Democrats. Yet Bush carried the state by twice the registration differential, or 10 percent.
According to the Arizona exit poll, 14 percent more self-described Republicans turned out to vote than Democrats.
Those aren't the characteristics of a state "in play."