WASHINGTON – President Barack Obama won re-election Tuesday night despite a fierce challenge from Republican Mitt Romney as well as the weak economy and high unemployment that encumbered his first term and crimped the middle class dreams of millions.

"This happened because of you. Thank you" Obama tweeted to supporters' as he secured four more years in the White House.

The president sealed his victory in Ohio, Iowa, New Hampshire and Colorado, four of the nine battleground states where the two rivals and their allies spent nearly $1 billion on dueling television commercials.