Stephen Miller fell out of the ugly tree and hit every branch going down ... so says one of the country's major political parties.

Yes, midterm elections are just a few months away ... and the political mudslinging has hit elementary school playground-levels with the official Democrats' X account telling Miller he's got no alibi .... 'cause he's U-G-L-Y.

The account lambasted Miller after he reshared a photo on Wednesday of Texas State Rep. James Talarico -- a candidate to represent the Lone Star State in the Senate -- and joked he's the party's "first transgender senate candidate."

Dems didn't take kindly to the comments ... and opted for the unsubtle approach -- writing, "shut up you ugly f***."

ICYMI ... Talarico won the Democratic primary race over Congressional Rep. Jasmine Crockett this month -- while Trump's endorsement of Ken Paxton helped him unseat incumbent Senator John Cornyn.

Republicans have ramped up their attacks on Talarico since he won the seat ... with the other Texas Senator, Ted Cruz, posting about him regularly on X -- along with the Senate Republicans tweeting that Talarico will dismantle the Texas oil and gas industry.

The election's on November 3 ... don't be surprised if the name-calling only intensifies.