– President Donald Trump attacked his own attorney general Wednesday, asking in a Twitter post why Jeff Sessions has not been investigating Democrats for Russian interference in the 2016 election.

“Question: If all of the Russian meddling took place during the Obama administration, right up to January 20th, why aren’t they the subject of the investigation?” he wrote. “Why didn’t Obama do something about the meddling? Why aren’t Dem crimes under investigation? Ask Jeff Session!”

In his tweet, Trump revived his offensive on Sessions, whom he once called “beleaguered,” and continued his dayslong Twitter comments on the ongoing special counsel’s investigation into Russian meddling. It was the latest instance of the president publicly criticizing federal law enforcement.

The president regularly uses Twitter to question why the Justice Department is not investigating his political opponents.

Trump has been questioning why the Obama administration did not do more to stop Russian interference, and he has said that his administration has been tougher on Russia than that of his predecessor.

Trump has denied that Russia was involved in the 2016 election meddling. But an indictment announced last week against 13 Russians and three companies described a sophisticated, multiyear Russian influence campaign designed to sow discord across the U.S. democratic process. On Tuesday, special counsel Robert Mueller announced charges against the 19th person in the sprawling probe that has dogged Trump’s presidency.

Trump does not think Sessions — one of his earliest supporters — has done enough to protect him from the Russia probe. The president has publicly said he never would have hired Sessions if he knew the attorney general would recuse himself from the Russia investigation.

The attorney general’s recusal last year was the first in a series of steps that led to Mueller’s appointment. Trump had once considered firing Mueller, but he backed down after the objection of a senior adviser.

In recent months, Trump has become more critical of federal law enforcement and has called senior officials at the FBI biased against him.