LyrArc Article Gist
The nearly unanimous support for president Trump in the impeachment inquiry from Republicans in Congress is a result of strong consistent support from a loyal base, strong fund raising in competitive races for members of Congress who supported Trump, and the sense that the whole process was flawed and part of partisan politics. There was also a sense among members of Congress in the House and Senate that the actions in Ukraine did not rise to the level of impeachable offense. 

Throughout the process from the beginning Mr. Trump, Mr. Pence, Mr. McCarthy minority leader in the House and Mr. McConnell majority leader in the Senate stayed engaged with individual members keeping together a tight knit community of legislators. As a result unprecedented action was seen in 2019-2020 with every single Democrat voting for impeachment and every single Republican voting against, and prominent members of each side showing outrage at events or how the proceedings were conducted.

Each side even seeing the impeachment inquiry as a strategic step towards the presidential election in 2020. Democrats looking for some slight advantage in the midwestern states that moved the election to Trump the last time. Republicans seeing this as a way to rally the base, play to Mr. Trump's strengths in persuasion, and to vigorously defend the economic achievements in international trade agreements and the economy.