It will cost him voters, not because he fought for his wall, but because he used federal employees as hostages to make his claim.
The Democrats may or may not yield on funds for a silly wall, depending upon what benefits a bipartisan bill may contain.
The 35 day shutdown had zero to do with whether Democrats would negotiate in good faith. There are willing, and have been willing.
But, they were not going to be bullied or extorted, knowing full well that the overwhelming number of Americans agreed that the downside to a federal shutdown far outweighed the benefits (if any) of a wall.