Senate Republicans may acquit Trump, but cannot save him from being discredited in the eyes of a majority of Americans.

Impeachment is a solemn process that impacts the American nation like no other political issue. At its core, the impeachment of a president is about determining whether that individual is fit to serve in the highest office of the land.

It is deliberately walled off from the question of that individual’s political appeal or public support. This is because, when drafting the American Constitution, our founding fathers inserted provisions to ensure that monarchical rule is never extended over the United States again.

During the impeachment process, the House of Representatives conducts an inquiry of, drafts, debates, and then passes Articles of Impeachment. The US Senate then acts as a jury of those articles, conducting a trial overseen by the leader of the third branch of government – the Chief Justice of the Supreme Court – ultimately deciding whether to remove the president from office or not.

On Wednesday, the House voted to impeach President Donald Trump for obstruction of Congress and abuse of power over his dealings with Ukraine, making him the third American president to be impeached.

Soon, impeachment will be in the hands of the Senate.

Embedded in the constitutional process of impeachment is an understanding that members of Congress, once elected, belong to the governing bodies in which they are serving and not to their own political parties. That is the burden of being an elected official – one must serve the entire country and honour his or her oath to the constitution.

Senators from the Republican Party, however, have already indicated that they will approach impeachment along partisan lines. Leading Senate Republicans such as Majority Leader Mitch McConnell and Lindsey Graham have pre-emptively stated that they would seek to cut the impeachment trial short and acquit the president.

Unfortunately, corruption of the impeachment process is surprisingly simple. There are no forcing mechanisms to require senators to be objective jurors. They must voluntarily choose to put their country first and to honour their constitutional oath. Nothing legally compels them to do so – just their integrity.

From an overall political perspective, impeachment is a net negative for President Trump. A Fox News poll reports that 54 percent of registered American voters support impeachment and 50 percent support his removal from office.

But this may not be enough to move the Senate, where 53 of the 100 Senators are Republicans and 67 votes are required to remove Trump. Many Republicans ultimately see their political fates tied to the president’s – in effect, choosing their political fortunes over their oaths to the constitution and the institutions in which they serve.

Yet, there is still a chance that some Republicans may not hold the partisan line, especially those who represent swing states, who are retiring, or who have already spoken out critically of Trump, such as Senators Mitt Romney (Utah), Cory Gardner (Colorado), Susan Collins (Maine), Lamar Alexander (Tennessee), Mike Enzi (Wyoming), Lisa Murkowski (Alaska), and Martha McSally (Arizona).

Setting the rules for the Senate trial is the next phase of the debate. These rules will define the procedures that will guide the trial, including determining whether there will be witnesses, whether more information from the White House will be sought, and the amount of time scheduled for debate. Senate Majority Leader McConnell will need 51 senators to support him, meaning that any three defecting Republicans can prevent his rules from taking effect. Currently, the pro-Trump camp is calling for limiting the number of direct witnesses to the president’s Ukraine moves. They also seek to make the process as short as possible.

Yet adding to the drama are the calculations of both Senate Minority Leader Chuck Schumer and House Speaker Nancy Pelosi – they are trying to push McConnell to call witnesses and have a fair Senate trial. Specifically, Schumer is seeking testimony from direct advisers to and witnesses of the president, such as acting White House Chief of Staff Mick Mulvaney, Secretary of State Mike Pompeo, and former National Security Advisor John Bolton.

Thus, the internal Republican fight will be over whether to have witnesses at the Senate trial, with Democratic pressure coming from both inside and outside the Senate Chamber. What is only guaranteed is that when the Articles are sent over to the Senate by the House, that the chief justice will call for them to be presented by the House prosecutors, and then for the president’s team to rebut the charges against him.

The downside risk for Trump right now is that if the Republican senators decide to limit the Senate trial, they will permanently stain Trump’s reputation, as acquittal will be perceived as more an act of political loyalty than justice. Questions about Trump’s behaviour will never be publicly aired and answered, and instead will be buried under the Republican desire to hide the testimony of direct witnesses who could exculpate the president.

Senate Republicans would be doing him no favour, as Trump would emerge deeply discredited in the eyes of a majority of Americans. Instead of being seen as innocent and vindicated, the president would be seen as protected and damaged. And Americans who support removal will see the country’s constitutional order threatened by a president who is no longer required to adhere to any rules.

However, if some Republicans decide to hold their integrity above partisanship and make sure that witnesses are called to the trial, the potential exists for everything to change.

There have been moments in American congressional history where one witness has changed everything. Take for example the McCarthy Red-Scare hearings of 1954, when witness Joseph Welch confronted Senator Joseph McCarthy, stating “have you no sense of decency?” in front of a nationally televised audience. That line was unexpected, and it destroyed not only McCarthy’s crusade but also his career.

This is what the pro-Trump camp is most afraid of and will do anything to prevent from happening.

Ultimately, regardless of what happens in the Senate, Trump will be damaged by the impeachment process. Either he gets acquitted by the Senate after an open trial with witnesses and still carries the label of “impeached”, or he gets acquitted without a fair trial and is seen as politically protected and above the law.

And looming, just ever so slightly, remains the prospect of him still suffering the political death penalty and getting removed from office, the first time ever for a president in American history.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.