GOP Sen. Ted Cruz Rafael (Ted) Edward CruzSenate GOP set to vote on Trump's Supreme Court pick before election Supreme Court fight pushes Senate toward brink Crenshaw looms large as Democrats look to flip Texas House seat MORE's lead over Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE (D) in the closely watched Texas Senate race has shrunk to 5 percentage points in a new poll.

Cruz is leading O'Rourke among likely voters, 51 to 46 percent, according to the Quinnipiac University Poll released Monday, with 3 percent of voters remaining undecided.

The narrow lead marks a tightening in the Senate race from an Oct. 11 Quinnipiac poll, which found Cruz leading O'Rourke by a 9-point margin, 54 to 45 percent.

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Peter A. Brown, assistant director of the Quinnipiac University Poll, said in a statement that O'Rourke remained "within striking distance," but "time is running out" if he is going to overtake Cruz.

"Sen. Cruz is ahead due to his winning the 'gender gap.' He wins men 56 - 39 percent, while Representative O'Rourke can manage only a 52 - 45 percent edge among women," Brown added.

Only 2 percent of likely voters who said they have decided whom they will support in next week's midterm election told Quinnipiac that they could change their mind.

The new poll was conducted from Oct. 22 to 28 and includes surveys of 1,078 likely Texas voters. The poll has a margin of error of 3.5 percentage points.

Cruz's lead in the Quinnipiac poll is narrower than his 6-point lead in a RealClearPolitics average of recent polling.

Democrats face a narrow path in an increasingly uphill battle of winning back the Senate majority.

In addition to keeping 10 seats in states won by Trump, including some races in which Democratic incumbents are behind in the polls, they would need to pick up two seats currently held by a Republican senator.

Democrats have focused their efforts on winning seats in Arizona and Tennessee, where GOP Sens. Jeff Flake Jeffrey (Jeff) Lane FlakeHow fast population growth made Arizona a swing state Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden MORE (Ariz.) and Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (Tenn.) are retiring.

They are also hoping to defeat Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.), who is the only Republican senator up for reelection in a state won by Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonThe Memo: Trump furor stokes fears of unrest Bloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close MORE in 2016.