The 2018 midterms seem likely to flip the US House of Representatives from a Republican to a Democratic majority. This change would impact the Trump/Republican agenda. Apparently much less likely, the US Senate could flip also. What would be the effect of a flip in both houses, should it occur, rather than the House of Representatives alone? And probably more of a theoretical question than anything likely, what would be the effect if the Senate flipped but the House of Representatives remained Republican?
I am interested in understanding the shift in power to act on an agenda and why a change in the House of Representatives alone is touted as a big change - why a change in the Senate doesn't seem to be given the same importance. Is it because it would have less of an effect, or because it has been deemed too unlikely to occur?