Updated at 12 p.m. Monday: Revised to include the margin of error.

Colin Allred has taken a four-point lead over Republican incumbent Pete Sessions in the 32nd Congressional District race, according to a poll completed Sunday night.

The New York Times Upshot/Siena College poll, conducted from Oct. 29 through Sunday, had Allred with a 46-42 lead, with 9 percent of respondents undecided. The poll surveyed 477 people and has a margin of error of plus or minus 4.7 percent, which means the contest could be a dead heat.

"About 9 percent of voters said that they were undecided or refused to tell us whom they would vote for," the poll document reads. "If they were to break 5 to 2 in favor of Republicans, that alone would be enough to change the lead in our poll, assuming we did everything else perfectly. (We could also be wrong on turnout or our sample could be unrepresentative. Or other voters could change their minds.)"

A previous Times/Siena poll in October had Sessions up by one percentage point.

"Colin got into this race to make Washington work for everyday people, not powerful special interests," said Allred's campaign manager, Paige Hutchinson. "The momentum this campaign has built shows we're not the only ones ready for a change, and in the closing days of this election, there's two things that matter: showing up and making your voice heard, then calling your friends and neighbors to ensure they do the same."

Caroline Boothe, Sessions' chief of staff and campaign spokeswoman, dismissed the relevance of the poll.

"People have been voting for more than two weeks. At this point, polling is meaningless," she said. "Right now, it's all about turnout and Pete is working relentlessly to remind people about his positive record of job growth and opportunity versus Colin's plans to take away the employee-provided health care of 505,000 residents of this district while raising taxes on working families and small businesses."

Allred says he wants to provide affordable and quality health care for all the residents of Texas. His plan includes making Medicare accessible to everyone. Sessions contends Allred is for socialized medicine. The issue is a flashpoint in their campaign.

The Dallas Morning News is part of The New York Times' effort to make the political polling process more transparent.

In the latest survey, Allred led 51 percent to 31 percent with independent voters and 48 percent to 41 percent among women, both thought to be key demographics in Tuesday's election. Both candidates had strong leads, with 90 percent or better, with their base party voters. Of the 477 voters surveyed, 309 said they had already voted, with 46 percent saying they favored Democrats compared to 45 percent who said they favored the GOP.

Sessions had a strong lead with white and older voters. The district, which went for Hillary Clinton in 2016, is changing demographically despite having some of Dallas County's wealthiest neighborhoods in the Park Cities and Preston Hollow.

The survey reflected other key factors in the race. Of those polled, 51 percent disapproved of President Donald Trump's performance, while 44 percent approved. Trump has endorsed Sessions, as has Vice President Mike Pence.

By a 49-44 margin, respondents preferred that Democrats control the House. And by a 49-44 margin, those polled wanted El Paso Congressman Beto O'Rourke to beat Republican incumbent Ted Cruz for U.S. Senate.

Sessions, 63, is the powerful chairman of the House Rules Committee. He's represented the district since 2003 and has been in Congress since 1997. In 2016, he didn't have a Democratic opponent.

Clinton narrowly beat Trump in the district, signaling that a strong Democratic Party candidate could be competitive against Sessions.

Allred, 35, is making his first run for elected office. He's a Dallas lawyer, former NFL player and worked in the Housing Department of President Barack Obama's administration.