Institution of State

In the US, the highest Institution of State is the Presidency of the US. For congressmen to not attend the inauguration of Trump is an intended insult to him and by extension an insult to this highest State Institution of the US.

Thankfully:

https://www.washingtonpost.com/powerpost/why-are-no-senators-boycotting-the-inauguration-national-ambition-is-part-of-it/2017/01/17/1675718e-dce6-11e6-918c-99ede3c8cafa_story.html?hpid=hp_hp-top-table-main_pkcapitol-930pm%3Ahomepage%2Fstory&utm_term=.f106dbf0d8d8

regardless of the motives of the Senators.