A weekend poll suggested Ted Cruz is winning this run-off by 10 points. It is the largest Cruz lead of the race and the Dewhurst campaign fought back Monday afternoon releasing a poll from their own campaign showing a Dewhurst victory.
On Monday afternoon, Cruz made his rounds on two national TV shows. Already on the verge of becoming a national political star, if Cruz pulls out a win Tuesday, he will be a conservative rock star.
"That's why we are winning right now. As you know, when we started this race, I was at 2 percent. We were never given a prayer," he said.
But it's not for certain and one long day from being over.
Outside an Austin Chick-Fil-A, Lt. Governor David Dewhurst predicted victory as well.
"I am proud of our position in the polls. Our polls have us winning. They've had us winning all along so I feel real good about tomorrow," he said.
What's clear is that voters don't want to be left out. Some political experts predicted the run-off on the last day of a very hot July would tamp down turnout.
In Harris County, 70,000 Republicans voted early or by mail in the runoff, meaning almost 9 of every 10 primary voters showed up for the run-off.
Rice University Baker Institute's Mark Jones predicts more than a million Texas Republicans will vote.
"Early on, the conventional wisdom was that higher turnout would have benefited Dewhurst and I still think that's the case but it's key to remember that higher turnout doesn't mean a Dewhurst victory," Jones said.
"A senator is not going to be elected Tuesday night," Democratic U.S. Senate candidate Paul Sadler said.
And then it's on to November. Sadler is one of the Democrats in Tuesday's run off. A former state lawmaker from East Texas, Sadler says he is frustrated that even Texas Democrats won't admit he's a possible contender in this race.
"The people of Texas have only heard one side of this debate. They've heard $26 million from Dewhurst and Cruz, they've not heard the other side of these issues. There is another story. I think it's the moderate view," he said.
Sadler's opponent Grady Yarborough did not respond to our interview request.