The news caught local party officials off guard, including Yakima County Republicans Chair, John Puccinelli.
"It's like going in the office and your boss comes up and says, you know what? Today's my last day. I'm leaving. What?!"
Yakima County Democrats Chair, Dany Adolf, had a different reaction.
"Once the shock wore off, it was a feeling of relief. That finally Doc Hastings is going to be out of the picture."
Doc Hastings' staff points to a long list of work done for Yakima County during his two decades in office. He pushed for increased water storage for the Yakima River basin and secured federal money for Valley schools.
He brought the House Agriculture Committee to Yakima to meet local farmers while the latest farm bill was being drafted, and he helped increase funding for vegetable and pest control research, as well as money to fight crime, drugs and gangs.
Yakima's Capitol Theatre got a new roof and air conditioning system.
"He was able to secure a $450,000 grant through the Economic Development Administration that we plowed right back in, so we could replace that," said Capitol Theatre Committee CEO Steve Caffery. "Without his help, we would not have been able to do that."
With Hastings' seat now up for grabs in November, both parties are gearing up for a fight. Yakima County Democrats are optimistic.
"This time around, we won't have the power of the incumbency working against us," said Adolf. "Whoever the Republicans put up against our candidate will be starting fresh, like our candidate is."
Local Republicans aren't worried.
"I think the Democratic Party's going to have a real hard time just holding seats they already have," said Puccinelli.
Whoever voters choose to fill Doc Hastings' shoes will need some pretty big feet.
Both party chairs told KIMA that possible candidates for Hastings' seat are already being considered. But, right now, they aren't providing any names.