The Republican race to succeed retiring Texas Sen. Kay Bailey Hutchison wasn't supposed to be tough. But it's become one of the hardest-fought and most expensive intraparty races in the country.
Early this year, the race was expected to be a coronation for Texas Lt. Gov. David Dewhurst, 66.
He's run the state Senate for the last decade, has a vast personal fortune to spend on the race and was the favorite of just about every establishment Republican in the state.
"David's the one candidate best prepared to make conservative change happen in Washington," Texas Gov. Rick Perry said in a political ad endorsing Dewhurst in May. "Don't let anyone tell you different. Our country needs him; so does Texas."
Dewhurst's opponent on Tuesday's ballot is Ted Cruz, 41, the former state solicitor general. "You know, when we started this campaign a year and a half ago," Cruz tells NPR, "there wasn't anybody in the state that thought I had a prayer. I was at 2 percent in the polls, and the margin of error was 3 percent."
If the primary had been held in March, the state's traditional primary month, many believe Dewhurst would have easily gotten the 50 percent needed to win the GOP match without a runoff. Instead, thanks to a lawsuit over legislative redistricting, the primary was pushed back to late May.
Dewhurst outpolled Cruz, 45 percent to 34 percent, but failed to top 50 percent. And that forced Tuesday's runoff.
GOP strategist Ted Delisi says moving the primary date changed the race.
"I think that there was always a potential for a competitive race," he says. "But it has become very competitive. And the reason for that is, that the non-Dewhurst candidates, and in this case Ted Cruz, have had the time to make their case."
Time for Cruz to meet more voters and time to build his name recognition across the gigantic state. Will Lutz, former editor of a prominent Texas conservative newsletter, says Cruz didn't have time to meet every voter, but he did the next best thing.
"For the past year and a half at least, he's been going to every conservative and Republican group that would listen to him," says Lutz." He has a stump speech that those audiences find attractive."
Cruz, the son of a Cuban-American father, gradually moved up in the polls. In a crowded primary, he was able to solidify the anti-Dewhurst vote. Then came a late endorsement from Tea Party favorite and former Alaska Gov. Sarah Palin. And finally, the Washington, D.C.-based conservative group Club for Growth spent about $2.5 million on attack ads.
That ad support coupled with Cruz's emphasis on reaching out to conservative bloggers and activists across the country gave him national attention, which dramatically affected his fundraising efforts, Lutz says.
"You will see people from all over the country giving money to Ted Cruz. He has made a splash in national conservative circles. Being on the cover of National Review magazine, which is a conservative commentary publication, is a real coup for somebody running for office in one state," Lutz says.
The money, endorsements and extra time to campaign led to a second-place finish in the May primary. Cruz's supporters are mostly from the grassroots activists-Tea Party branch of the GOP.
The Dewhurst campaign has failed to generate that same emotional fire. In an interview with NPR, Dewhurst says he has been calling as many people as possible to make sure his supporters don't skip the runoff.
"We have polled and polled and there are substantially more David Dewhurst voters in Texas that we've been able to identify, than Ted Cruz voters," says Dewhurst. "But again — it's a question of turnout."
Recent polling shows Cruz has the momentum, and he spent the weekend trying to build on that advantage, campaigning with Palin and former Pennsylvania Sen. Rick Santorum, who garnered significant conservative support while running for the Republican presidential nomination this year.
Cruz says Tuesday's contest will prove whether the conservative grassroots matter.
The Democrat on November's ballot will also be decided Tuesday, when former state Rep. Paul Sadler and retired teacher Grady Yarbrough square off. But Texas has not elected a Democrat to a statewide office in 18 years.