President Donald Trump and Democratic challenger Joe Biden are battling it out for the White House, with polls gradually closing across the United States Tuesday -- and then a long night of waiting for results ahead.

The first results are trickling in, with US media projecting wins for the Republican incumbent so far in 19 states including Indiana, Kentucky, Missouri, Ohio and Tennessee -- all states he won in 2016.

Biden has captured 17 states including his home state Delaware and big prizes California and New York, as well as the US capital. As with Trump, so far, all states claimed by Biden were won by Democrat Hillary Clinton in 2016.

So far, that gives Biden 213 electoral votes and Trump a maximum of 138, because Nebraska splits its electoral votes based on congressional district (see note below).

The magic number is 270. Observers expect the hotly contested race for the White House to come down to a handful of key battleground states that have yet to be called.

The following is a list of the states won by each candidate and the corresponding number of electoral votes, based on the projections of US media including CNN, Fox News, MSNBC/NBC News, ABC, CBS and The New York Times.

TRUMP (138)* Alabama (9)

Arkansas (6)

Idaho (4)

Indiana (11)

Kansas (6)

Kentucky (8)

Louisiana (8)

Mississippi (6)

Missouri (10)

Nebraska (5) *

North Dakota (3)

Ohio (18)

Oklahoma (7)

South Carolina (9)

South Dakota (3)

Tennessee (11)

Utah (6)

West Virginia (5)

Wyoming (3)

BIDEN (213) California (55)

Colourado (9)

Connecticut (7)

Delaware (3)

District of Columbia (3)

Hawaii (4)

Illinois (20)

Maryland (10)

Massachusetts (11)

New Hampshire (4)

New Jersey (14)

New Mexico (5)

New York (29)

Oregon (7)

Rhode Island (4)

Vermont (3)

Virginia (13)

Washington (12)

* Nebraska splits its five electoral votes -- two electors are assigned based on the plurality of votes in the state, and the other three are awarded based on congressional district. Biden could eventually peel at least one of these votes away.