Group includes prominent lawmakers from both parties. http://www.rollcall.com/news/politics/44-sitting-members-congress-accepted-donations-trump
Traditionally, candidates set up fund raising committees and use those to donate to individual house and senate candidates. If a candidate is self funded, he/she would donate directly. The amounts are trivial.
I'm wondering if any of the politicians who are boycotting the inauguration have accepted donations from Trump and if so are they returning them.