BLUE ON BLUE: Progressives fume at Buttigieg, warn him not to attack Warren at debate.

Buttigieg, who has emerged as a center-left contender for the Democratic presidential nomination, has drawn the ire of progressives in recent days for remarks viewed as swipes against more liberal contenders like Warren and former Rep. Beto O’Rourke (D-Texas).

“It’s sad to see the potential self destruction of @PeteButtigieg, a rising star,” tweeted Adam Green, a cofounder of the Progressive Change Campaign Committee, which backs Warren. “Tuesday will be a key trajectory moment. Does he attack the next President of The United States or take the high road and make positive waves by adding his unique voice to progressive issues of the day?”

The warning comes as Buttigieg has been rising in Iowa polls, positioning him to become a potential top-tier challenger to Warren and former Vice President Joe Biden.