In Texas, the GOP primary to fill Kay Bailey Hutchison's U.S. Senate seat has become  a costly and bitter fight that may not end today.

Texas election code stipulates that candidates must receive at least 50 percent of the vote to win their party's nomination outright. If no candidate reaches that mark, the top two candidates go into a runoff, which would take place  July 31.

Polls show David Dewhurst, the state's lieutenant governor, as ahead in the race but shy of the 50 percent mark. Dewhurst's biggest challenger is Ted Cruz, an up-and-coming Tea Party star and the state's first Latino solicitor general. Heading into tonight, a Dewhurst-Cruz runoff seems very possible.

Neither candidate's ultimate victory would put the race in play, though. Whoever wins will most likely be the next senator from Texas, which makes this primary contest all the more important.

The race has so far received a great deal of attention, in part because of the amount of money that has been spent - upward of  $25 million, more than any other Senate race in the country this cycle.

If the race goes into a runoff, spending is likely to increase greatly.

Dewhurst has had the financial advantage so far. Both candidates report raising around $6 million in individual contributions, but the lieutenant governor has spent $8 million from his own pocket on his bid so far, according to his campaign's  disclosures.

Big spending in a competitive statewide race in Texas is inevitable. Because Texas is such a large state, candidates have to take to the airwaves. And major media markets, such as  Dallas and Houston, are among the most expensive in the country.  The longer the race goes on, the closer it gets, the more money will be spent.

And it's not just the spending. Ted Cruz's candidacy  has also brought attention to the race.

Cruz, 41, is a rising Tea Party star. A crusader against "out of control" spending, he's been endorsed by the likes of Sarah Palin, Sean Hannity, Jim DeMint and Rick Santorum. Cruz, whose father was Cuban-American, is often is compared to another Tea Party star, Sen. Marco Rubio, R-Fla. If he were to win, he'd be the first Latino senator from the state of Texas.

"Our nation is at a crossroads. We're going broke," Cruz told ABC News. "If we don't stand up and stop out of control spending and crushing debt, we're gonna lose the country. And that's precisely why I'm running."

Cruz is straight-talking and unapologetic. When the Dallas Morning News and the Houston Chronicle endorsed Dewhurst, Cruz took it in stride.

"I told the Dallas Morning News  if you are looking for an establishment moderate to go to Washington, to work across the aisle, to cut deals, increase spending and increase our debt, I ain't your guy," Cruz said.

"My view on compromise is the same as Ronald Reagan. What do you do if they offer you half a loaf? Answer, you take it, and then you come back for more. I am perfectly willing to compromise if  and only if  we are willing to move the ball forward  and shrink the size of government," he said.

The race has been categorized as an establishment vs. Tea Party battle. Cruz himself has played a hand in driving that narrative, but Dewhurst has challenged the label.

"Some of my opponents get confused regularly and say things that simply aren't true," Dewhurst told ABC News.

"I am proud of the fact that I negotiate, but I don't compromise my values. As a life-long businessman, I've done a lot of business deals and I've never had anyone accept my initial offer when I was proposing a business deal. What resulted was negotiations, and I never compromised my company. The same is true in the political arena in which I will negotiate, but I won't compromise my political principles."

Although Cruz certainly fits the mold of a Tea Party candidate, it bears noting that Dewhurst's record is much more conservative then other "establishment" candidates who have fallen to Tea Party challengers such as Dick Lugar in Indiana or Mike Castle in Delaware. Dewhurst has the endorsements of Rick Perry and Mike Huckabee, as well as the backing of many anti-abortion rights organizations in the state.

"It's impossible to categorize me any other way than the strongest proven conservative in this race," says Dewhurst. "Plus, I'm the only candidate in this race who has a solid socially conservative record. I have passed more 'pro-life' legislation in the last nine years than has ever been passed in state of Texas."

If the race does go into a runoff, many political officials in the state believe Cruz would probably benefit from the inevitable decrease in turnout in the July 31 race. There is some question as to whether or not supporters of former Dallas Mayor Tom Leppert, currently polling in third place, would turn out for Dewhurst, giving him a boost.