Considering where Ted Cruz started, and even where he was after the first round of voting, a victory by the Tea Party-backed candidate would be a major upset.

PPP:

PPP's final poll of the Republican Senate runoff in Texas finds Ted Cruz opening up a 52-42 lead, an increase from our survey two weeks ago that found him ahead 49-44.

Cruz's victory is driven by 4 things: the Tea Party, the enthusiasm of his supporters, a generational divide within the Texas Republican ranks, and the lack of regard the party base currently holds for Rick Perry.

Cruz is ahead by a whooping 75-22 margin with Tea Party  voters, more than making up for a 56-39 deficit to Dewhurst with voters who don't consider themselves members of that movement. There has been too much of a tendency to ascribe any Republican primary upset over the last few years to Tea Party voters, but this is one case where it's well justified.

Cruz has a 63-33 advantage with voters who describe themselves as 'very excited' about voting in Tuesday's runoff election. He also has a 49-45 advantage with those describing themselves as 'somewhat excited.' The only reason this race is even remotely competitive is Dewhurst's 59-31 lead with voter who say they're 'not that excited' about voting. It's an open question whether those folks will really show up and if they don't it's possible Cruz could end up winning by closer t0 20 points.

In a low turnout election as this one promises to be, voter enthusiasm is key. In that respect, Cruz is far ahead and could very well cruise to victory tomorrow.