Ted Cruz — a Tea Party upstart who was considered a long-shot to upset GOP establishment favorite Lt. Gov. David Dewhurst in the Texas Senate primary run-off — has surged ahead in polls three weeks ahead of the vote. One survey has Cruz leading 47 percent to 38 percent — a massive turnaround since he lost by 10 percentage points in the May 29 primary. (Even though Cruz lost, he still managed to force a run-off.) Dewhurst, who has poured more than $10 million of his own money into his campaign and is backed by Gov. Rick Perry, looked almost unbeatable for a time. But national Tea Party groups, energized by their defeat of six-term GOP moderate Sen. Richard Lugar in Indiana, rallied behind Cruz, a former state solicitor general who's been hailed as this year's "biggest Tea Party rock star" and the next Marco Rubio. Will Tea Party enthusiasm put Cruz over the top?

Cruz may be headed for victory: The latest polls are "a huge deal for Cruz," says Katrina Trinko at National Review, and it looks as though his relatively strong showing in the May primary inspired some Dewhurst supporters to give the insurgent a second look. Or "perhaps the intense grassroots enthusiasm for Cruz is paying off." Whatever the reason for this 19-point swing, "the momentum on the ground" is all going Cruz's way.

"Cruz ahead by 8 points in new poll"

Sorry, Tea Party passion isn't enough: Dewhurst built a "solid base" of conservative support over 13 years in politics, says Will Weissert of The Associated Press. He's a "known quantity" with a popular governor, Rick Perry, on his side. Cruz is counting on Tea Party enthusiasm, but high-energy rallies alone won't "get voters to turn out in the dog days of summer," and that's what Cruz needs to win.

"Ted Cruz, Texas Senate candidate, hopes Tea Party passion will carry him to GOP run-off victory"

Dewhurst is beatable, but it won't be easy: The run-off is still three weeks away, says Erick Erickson at RedState, and while one poll has Cruz way ahead, another — by Democratic-leaning Public Policy Polling, which "has no dog in the fight" — shows a tight race. "Dewhurst has millions of dollars in advantage over Cruz." So if conservatives want to put another leader committed to small government and low taxes in the Senate, "it is time to pony up for Ted Cruz."

"New poll has Ted Cruz up. Conservatives need to pony up fast"

Read more political coverage at The Week's 2012 Election Center.