Voting begins in US mid-term elections in less than 6 hours. Candidates are making their final push in bruising campaigns that promise a tight race.

At stake are all 435 seats in the House of Representatives and 37 of the 100 seats in the Senate. Democrats currently hold 255 seats in the House, and President Barack Obama's party is expected to lose that majority.

A Reuters poll indicates that Republicans will pick up 52 seats, leaving them with a 27-seat majority. And Gallup's final pre-election poll gives Republicans a 55 percent to 40 percent lead over Democrats in a congressional ballot test among likely voters.