Democratic U.S. Senate candidate Beto O'Rourke made his last appearance in Austin before Tuesday's election, imploring a crowd of 5,000 at Pan American Neighborhood Park on Sunday to devote themselves in the time remaining to help him pull off an upset in the first statewide election in Texas in a generation in which a Republican victory is not a foregone conclusion.

"Over the next 54 hours, I'm asking you to give me every waking moment of your life," said O'Rourke, a three-term congressman from El Paso.

"Let's make sure we have done everything within our power to talk to every single Texan who yet has a chance to decide this election, to decide the future and the fortune and the fate, not just of Texas, not just of this country, not just of this generation, but the generation to follow," O'Rourke said.

U.S. Sen Ted. Cruz, the Republican, remains the front-runner, consistently leading in the polls. But his margin, which a few weeks ago was growing, has narrowed of late, and record-shattering early voting numbers have added an unfamiliar element of uncertainty in a state hasn't elected a Democrat to statewide office since 1994.

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Cruz, who campaigned Sunday in the North Texas suburbs of Bartonville and Fairview, spoke about moderate and conservative Democrats who are voting for him because the Democratic Party has moved too far to the left — a standard part of his stump speech.

“For a long time in Texas, there have been millions of conservative Democrats, millions of moderate Democrats, and they are looking now at the national Democratic Party that’s getting more and more extreme, getting more and more radical, more and more crazy,” Cruz said in Bartonville.

On Sunday, he tweeted a video offering individual testimony to that, with an intro quote from the British writer and theologian C.S. Lewis: "We all want progress, but if you are on the wrong road, progress means doing an about turn and walking back to the right road. In that case, the man who turns back soonest is the most progressive."

O'Rourke told the Austin crowd that early voting in Travis County had soared from 143,000 in the last midterm election to 368,000 this year.

"The numbers that are incredible here are the 12 percent of the early voters (who) were not registered as of March 16, and this is the first time in our history when the (voters) under 35 is exceeding the (voters) over 55," said Austin Mayor Steve Adler, who attended the rally. Adler said that 34.5 percent of the early voters in Austin were under 35, and 31.5 percent were over 55.

"What (O'Rourke) needs to be able to win was have different people show up to vote, which is what every candidate says they are going to make happen, and no one ever does, except in this race it is evident there are people voting who have never voted before," Adler said. "No one really knows who they are ... so I don't think anyone can know what's going to happen in this election on Tuesday."

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The Texas Senate race, which was featured on "60 Minutes" Sunday night, continues to intrigue and confound national pundits and prognosticators.

Early voting in Travis County and the state's other largest counties was nearly as high as early voting in the 2016 presidential election. In Williamson County, early voting during the 12-day period that ended Friday exceeded the early vote in 2016. But in Hidalgo and Cameron counties, heavily Hispanic and reliably Democratic, turnout lagged, with Hidalgo at 77 percent of the 2016 early vote and Cameron at 81 percent of the 2016 early vote.

That suggests that O'Rourke has not roused the Hispanic vote, at least in the Rio Grande Valley, and his hopes rest more on having appealed to younger, more liberal white voters who like his progressive politics and post-partisan style.

Republicans believe that O'Rourke's campaign also has stirred Republican voters to turn out in record numbers to keep Texas red.

"Higher turnout is better for the GOP," said Dave Carney, chief strategist for Gov. Greg Abbott's campaign, which is leading the Texas GOP turnout effort.

While O'Rourke boasted in Austin that his campaign had knocked on a million doors so far — and hoped to reach another million voters through Tuesday — Carney said a million doors knocked means about 200,000 knocks answered.

"We've knocked on more than 7 million doors," Carney said. "We will let the results on Tuesday speak for themselves."