"Law enforcement officers and prosecutors may never select the timing of investigative steps or criminal charges for the goal of affecting any election, or for the objective of giving an advantage or disadvantage to any candidate or political party", reads a 2016 Justice Department memorandum issued by then-Attorney General Loretta Lynch, which mirrors language issued by previous attorneys general ahead of federal elections.
The president's striking suggestion that the Justice Department consider politics when making decisions showed his disregard for the agency's independence.
"Two long running, Obama era, investigations of two very popular Republican Congressmen were brought to a well-publicized charge, just ahead of the midterms, by the Jeff Sessions Justice Department", Trump tweeted from the White House.
In an interview with Bloomberg on Thursday, Trump said Sessions would remain in his job at least until the November midterm elections. But in what is expected to be a charged debate over Sessions's successor - a debate likely to try even some Republican senators wary of Trump's maneuvers - tweets like the ones Sunday aren't exactly going to tamp down the idea Trump is searching for a political crusader to lead the DOJ.
The congressmen he referred to in two combative tweets were Reps.
Both men are key Trump supporters. Trump did not have any public events Monday.
Trump stumps for GOP Senate hopeful Braun in Indiana
But flipping the Senate remains a much tougher prospect, given that 10 incumbents are running in states Trump won. Some of the issues he's raised have either already been examined or are being investigated.
The Hunter investigation began in June 2016, according to the indictment.
Ben Sasse (R-Neb.) released a statement saying, "The United States is not some banana republic with a two-tiered system of justice - one for the majority party and one for the minority party". "Really sick!" the commander-in-chief ranted in a second tweet.
"The Democrats, none of whom voted for Jeff Sessions, must love him now".
The investigation into Hunter began more than a year ago, apparently during the early stages of Trump's own administration - not President Barack Obama's.
The tension between Trump and Sessions boiled over recently with Sessions punching back, saying that he and his department "will not be improperly influenced by political considerations".
Still, Mr Sessions has made clear to associates that he has no intention of leaving his job voluntarily despite Mr Trump's constant criticism.