WASHINGTON: Republicans made a final push Sunday to prevent a predicted thumping in US midterm elections where Democrats are gunning to win Congress and impose a first political check on President Donald Trump's unprecedented pursuit of power.

Polls show Democrats are all but certain to take the majority from Republicans in the House of Representatives in Tuesday's vote and have a shot at winning the Senate.

But after a decade of Trump defying political gravity and two years of a second presidency in which he has ridden roughshod over every norm, Democrats remain nervous.

"Nauseously optimistic," Democratic Senator Raphael Warnock told CNN to describe the mood.