Democrats caused the shutdown, they shut down the government over DACA. So they will get the blame
People said the shutdown wont be a big deal because the GOP rebounded in 2014 and won. Whn prior to November the stories about Obamacare rollout made people forget about the shutdown plus enthusiasm went up for the republicans prior to the election because they were the party not in the White House.
Then if you remember the 1995 Shutdown rather than helping the GOP, that along with the Oklahoma city bombing events made Clinton's popularity revive for him to win in 1996.
I fear that if the shutdown lasts longer then it will be '1996' for Trump instead of '2014'.