There would be a very small amount of praise from the right, a very small amount of jokes about her being a phone-it-in first lady from the left, and both would be overshadowed by an overwhelming amount of indifference by everyone.
It's just an assumption to say that both sides are the same. Barbara and Laura Bush, for example, were not demonized like Hillary Clinton and Michelle Obama.
Moreover, generally democrats don’t stoop as low as republicans. Republicans attacked Chelsea Clinton when she was like 11—Rush Limbaugh was calling her ugly. Can you imagine any democrats calling Barron ugly or something as vicious? How about how Fox News harassed Obama’s kids? You’d never see that on CNN. Republicanism is a morally bankrupt ideology.
In Norway none of this is very controversial, and fast food companies have little political influence. Money in Norwegian politics is quite restricted. Not sure how it is now, but usually you could not pay for political TV ads.
If you wanted to get on TV you would have to join a political TV debate of which there are usually a lot of.
The issue is harming children's nutrition to score political points.