Kacey Musgraves is letting Kristi Noem have it after the ex-Secretary of Homeland Security threw some shade her way.

Noem had attempted to pit the country singer against rising star Ella Langley while endorsing Texas' conservative senate hopeful Ken Paxton over Democrat James Talarico.

Noem slammed the fact that Talarico showed up to Kacey's Dallas concert, saying ... "I'll take @ellalangleymusic over Kacey Muscraves any day. And if I'm choosin' Texas, I'll take Ken Paxton over James Talarico."

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But Kacey fired back at Noem with a brutal response, saying ... "I don't think you have a dog in this fight but if you did you have shot it."

The singer's zinger is a direct reference to Noem infamously shooting and killing her 14-month-old pup, Cricket, after she said he was untrainable.

Both artists are currently on tour and the Texas midterm race is still weeks away ... looks like the dog days are far from over in this feud.