Donald Trump has moved back into the lead of the 2016 Republican presidential contest, while Ted Cruz has surged into second place, according to a new national NBC News/Wall Street Journal poll.

Meanwhile, Ben Carson — who was ahead in the poll back in late October — has dropped 18 points to fourth place in the GOP race.

In the current poll, Trump is the first choice of 27 percent of Republican primary voters (up four points since the last poll).

He's followed by Cruz at 22 percent (up 12 points) and Marco Rubio at 15 percent (up four).

But Carson is now in fourth at 11 percent (down 18 points) — and much of his support has transferred to Cruz.

Indeed, while the poll shows Carson dropping 23 percentage points among "very conservative" Republican primary voters since October, it has Cruz up with this group by an equal amount.

"Where Cruz picked up is where Carson lost ground," says Democratic pollster Fred Yang of Hart Research Associates, who conducted this survey with Republican pollster Bill McInturff.

"This is a real shift," McInturff adds.

Rounding out the GOP field are Jeb Bush (at 7 percent) and Carly Fiorina (at 5 percent). No other Republican candidate gets more than 3 percent.

When the field is winnowed to just five GOP candidates — Trump, Cruz, Rubio, Carson and Bush — Trump leads the pack at 30 percent among Republican primary voters.

He's followed by Cruz at 24 percent, Rubio at 21 percent, Carson 13 percent and Bush at 9 percent.

The NBC/WSJ poll was conducted Dec. 6-9 of 400 Republican primary voters (by both landline and cell phone), and it has a margin of error here of plus-minus 4.9 percentage points.