Mega Millions jackpot jumps again to $636 million

There's just no stopping the Mega Millions jackpot, which jumped again Tuesday to $636 million, from $586 million, nearing the all-time record for the largest jackpot.

Lottery officials set the prize amount based on a forecast of ticket sales, but as the jackpot continues to grow -- no winner has matched all six Mega Millions numbers since October -- sales have outpaced the forecast, resulting in the upwards revisions.

The jackpot for Tuesday night's drawing is closing in on the largest in history, a $656 million prize split three ways, sold in March 2012.

But because of a change in rules making the odds of winning even slimmer than they already were, the lottery could potentially reach $1 billion by Christmas.

Mega Millions