Incumbent Republican Sen. Ted Cruz leads Democratic Rep. Beto O'Rourke by one point in their Texas Senate race, putting the two in a dead heat for the seat.

An Emerson College poll puts Cruz at 38 percent compared to O'Rourke's 37 percent among registered voters. Twenty-one percent are still undecided, according to the poll, conducted Aug. 22 -25.

Emerson's poll comes one week after a Marist/NBC News poll found O'Rourke four points behind Cruz. O'Rourke has seized national attention as he's brought in sizable fundraising hauls, besting Cruz in the second quarter. And last week, a video of the El Paso congressman answering a question about NFL players kneeling in protest of police violence against African-Americans went viral.

“I can think of nothing more American than to peacefully stand up or take a knee for your rights anytime, anywhere, anyplace," said O'Rourke.

In response, Cruz launched an ad Monday about standing for the national anthem, asking voters "in November, where will you stand?"

[Also read: Trump attacks NFL: ‘Do they not have a clue?’]