Last minute efforts by the Democrats to call witnesses in Donald Trump’s impeachment trial have proven unsuccessful, leaving the stage set for his acquittal.

The Democrats are currently outnumbered in the Senate by 47 to 53 and have urged the Republicans to rebel and vote with them today.

They need four “waverers” to come forward as witnesses in a bid to gain testimonies that would prolong proceedings for another few weeks.

Republican Lamar Alexander initially said he would vote with the Democrats as the third rebel, but reneged on his position after stating that although the Democrats had proved Mr Trump acted inappropriately, it was not an impeachable offence.

Republicans Mitt Romney and Susan Collins have indicated their support and potential vote with the Democrats, however, Mr Alexander’s withdrawal has weakened the plan.

“The question then is not whether the president did it, but whether the United States Senate or the American people should decide what to do about what he did,” he added.

Chief Justice John Roberts could change the vote or allow the motion to fall, meaning no witnesses, if there is a 50-50 tie.

The Republicans will decide if Trump should be convicted if John Roberts’ vote fails. However, 20 Republican senators would need to switch sides to do that, leaving the President likely to be acquitted.

Speaking at a campaign rally in Des Moines, Donald Trump has remained optimistic about his time in office, despite the ongoing trial: “We’re having probably the best years we’ve ever had in the history of our country — and I just got impeached!”