I know that the other impeachments in US history (plus the near-impeachment with Nixon) are all considered controversial events and decisions, or at least were at the time in Nixon's case. Johnson's impeachment trial itself was very partisan, with the vast majority of Republicans and no Democrats in both houses voting "yea" to impeach.
Was this the view in the general public? Did the average voter believe that Johnson was criminal and had to be removed, that this was just a baseless political stunt and power-grab, or something in between?
In addition, in the general scholarly historical consensus (if there is one), which was it? Reading the summary on Wikipedia gives me the impression that it was a political stunt (using a veto-proof majority to pass a likely-unconstitutional law to limit the President's power, that you expect him to break, and then impeach him for breaking it); is this an accurate way of looking at it?
It was more of a product of political infighting than anything else. The congress and the president had a political war for 2 years by the time impeachment came around. The problems had begun to arise by the time the civil war came to its end. Southern racism and inability to accept the new laws had led to a push against northern influence. This happened both at a political and local level, with different organizations and bands of people roaming the countryside and suppressing fredmen.
In washington there was a great fallout over the question on how to deal with these events. The republicans, espically the radical faction led by wade and davis, wanted to impose northern ideas of equality at any cost, and if nessescary with the help of the army, on the south. The less radical republicans had no modern idead of equality, but still had an interest in pacifying the south. The democrats hat no such intentions and wanted to leave the south to their own devices. President johnson, born as a poor white southener, was of the firm opinion that poor white farmers in the south were the real loosers in all this abd prioritized them, while paying no attention to the freedmen.
With the racist black codes being implemented in many southern states, and a steady increase in the violence, brought about by the KKK and others, there was still no presidial response in sight. Over time this led to a political rift which only grew in size with every new massacer and upheaval in the south. With the wade-davis manifesto and other republican responses there was eventually no way of reuniting the parties again left.
By the time the impeachment came around the congress had taken over and the south was divided into 5 military districs and subdued by the army. The impeachment itself was mostly sought to be a signal. In the end it was barely stopped, because a radical republican (wade) wpuldve replaced him and there was a great fear that this vote would damage the image of democracy for a long time.
The reactions themselves were very split. Most southeners either liked johnson or saw him as a lesser evil and were highly offended by it. In the north the opinion was equally split, with radicals and republicans wanting him to be gone. Some democrats saw him as incompetent, others saw this as jsut another republican strategy. While the opinion on his impeachment was very split, it is worth poiting out that widespread racism (both in thw north and the south), the difficult situation of the freedmen and the political turbulences overshadowed the politics of reconstruction. The impeachment was jsut another step which had never been taken before and was seen as highly radical.
Sources: congressial testimony, washington, 1871 Tennessee legislation 1868 Testimonies and diaries from multiple southeners. Some of these can be accessed through the library of congress
Literature: Shawn leigh, Alexander reconstruction violence and the Ku Klux Klan hearings Martinez, michael, carpetbeggars, cavalry and the Ku Klux Klan Flitzgerald, michael w. Reconstruction in alabama