The economy is not a problem. The Dems might have run on it instead of the war back in 2002, when we actually had a recession, but that is long past and there is nothing there anymore. Pols just can't adjust to economic realities and talk about real issues, their spin machines must allege crap about the economy because their entire ideological structures are built around their crackpot economic prescriptions.
As for immigration, that is a real political issue, but not because it has any massive economic impact or is ruining the economy. We have an assimilation problem with Mexican immigrants and a law enforcement problem, and we ought to deal with both, forcefully. Which has nothing to do with highly skilled and desired legal immigrants for all over the world, who want to come here to work (not loaf), and present no such problems. By all means, hold Congress's feet to the fire over enforcement and welfare eligibility and English, I'm with you 100%.
When you try to turn those things into opposition to *all* immigration, when you try to make it some economic idea that any immigration impoverishes us, you are just wrong, and we part company. Legal immigration of skilled and willing workers helps our economy. It built our economy from nothing to the envy of the world. We do not need to kill that goose, to deal with the border problem.
The main reason why Democrats are doomed to lose is because they abandoned the previous New Deal platform and replaced it it with atheism, abortion and "gay marriage". Otherwise they would be winning by landslides like FDR did. On issues like globalism, open borders and "free" trade they do not differ from Republicans.