Staunch conservative allies of President Donald Trump erupted in anger and incredulity after Democrats announced the president had agreed to pursue a legislative deal that would protect thousands of young undocumented immigrants from deportation but not secure Trump's signature campaign promise: building a massive wall along the US-Mexico border.

As midnight neared, social media accounts came alive as elected officials and activists on the right dashed off tweets and posts to share their shock.

And in between those posts, there was a flurry of fuming calls and text messages - a blaring political fire alarm among Trump's die-hard supporters.

"The reality is sinking in that Trump administration is on the precipice of turning into an establishment presidency," Sam Nunberg, a former Trump campaign adviser, said in an interview early Thursday morning, local time.