Voters decide pivotal congressional, gubernatorial races Tuesday

Washington (CNN) -- The most expensive midterm elections in history finally began Tuesday, as voters started casting ballots to decide who goes to Congress and governors' offices.

With all predictions, the election is considered a referendum on both the Democratic-controlled Congress and President Barack Obama's first two years in office.

Polls indicate a dissatisfied electorate could clean house -- literally -- by tossing out the Democratic majority in the House of Representatives and possibly doing the same in the Senate.