How Trump gets to $8 billion to build southern border wall

President Donald Trump says he will spend about $8 billion to build a wall on the U.S.-Mexico border. It's a far greater sum than the roughly $1.4 billion Congress set aside for that purpose in legislation Trump is expected to sign to prevent another partial government shutdown.

Trump has declared a national emergency on the southern border and is using his executive authority to go around Congress and siphon money from other government accounts.

Here's a breakdown of the $8 billion, according to acting White House chief of staff Mick Mulvaney:

—$1.375 billion included in the government funding bill awaiting Trump's signature.

—$3.6 billion from military construction funds.

—$2.5 billion from Defense Department counterdrug activities.

—$600 million from the Treasury Department's asset forfeiture fund.