On the campaign trail, Donald Trump repeatedly said he would not cut government-provided health and welfare benefits - and Bernie Sanders is determined to make sure nobody forgets it.
Mr Sanders printed off a 2015 tweet from the United States President-elect, blew it up to poster size and took it into the Senate on Wednesday (US time).
It reads, quite plainly: "I was the first & only potential GOP candidate to state there will be no cuts to Social Security, Medicare & Medicaid."
"I think it is interesting that we listen to what Donald Trump said during the campaign... and more importantly, Republicans listen and hear what their leader had to say about these issues," Mr Sanders told the floor.
"This is what Donald Trump said. He didn't say it once in the middle of the night, he didn't say it in an interview. It was a central part of his campaign."
Mr Trump aside, Republicans want to make cuts to social security, Medicare and Medicaid. Social security is the US version of welfare, while Medicare helps fund healthcare for over-65s, and Medicaid for Americans of all ages.
Mr Sanders called on the billionaire businessman to either veto any decisions made by the Republican-dominated Senate to cut entitlements, or admit he was lying the whole time.
"Mr Trump was right, and millions of people voted for him on the belief he would keep his word.
"If all that he was talking about was campaign rhetoric, then what he was obliged to now is tell the American people [he] was lying...[he] had no intention of keeping [his] word. If that's what he believes, let him come forward and say that.
"But if...he was sincere, then I would hope that tomorrow, or maybe today, he would send out a tweet and tell his Republican colleagues to stop wasting their time."
The odd sight of a giant tweet gracing the floor of the Senate inspired a competition on website Gizmodo.
Other Twitter users also got in on the fun.
Mr Trump regularly uses Twitter to make announcements, mock his opponents and promote his allies.