Everything's bigger in Texas, and today's state and presidential primary is no exception.

Mitt Romney is expected to reach (and surpass) 1,144 delegates tonight-the magic delegate number needed to officially win the GOP nomination. With 155 delegates at-stake, Texas's GOP primary is the largest delegate prize in the contest so far-the second largest overall. California will offer the most delegates on June 5.

Bigger than the delegate math however, is the Republican Senate primary, which is so far the most expensive Senate race in this election cycle. Some $25 million has been spent on behalf of the candidates seeking to fill the seat left open by Kay Bailey Hutchison's retirement. Although the list of candidates on the ballot is long, the race is mostly considered to be contained to David Dewhurst, the state's lieutenant governor, and Ted Cruz, the former solicitor general.

The Dewhurst/Cruz race has been largely framed as an establishment vs. Tea Party battle, with Dewhurst labeled as the establishment candidate, and Cruz appearing to claim the tea-party mantle. Cruz has received endorsements from national tea party figures like Sarah Palin and Jim DeMint, but Dewhurst has numerous conservative endorsements as well such as Rick Perry and Mike Huckabee.

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

Polls show Dewhurst, 66, in the lead and Cruz, 41, in second place, but Dewhurst is shy of 50 percent. A Dewhurst/Cruz runoff seems very possible at this point.

Over 200,000 ballots have already been cast through early voting, according to calculations from the Texas Secretary of State.

The Democratic Senate primary looks likely to go to a runoff as well, with polls showing a close contest between former state Rep. Paul Sadler and Sean Hubbard, a 31-year-old newcomer to the Texas political stage. But that race has received considerably less attention and funding, in large part because Texas is viewed as a solidly Republican state.

Democrats also hold their presidential primary in Texas today. Obama will be joined on the ballot by several challengers, including John Wolfe, the Tennessee lawyer who received 42 percent of the vote in the Arkansas primary. Obama's approval rating is not as low in Texas as it is in Arkansas, Kentucky or West Virginia, but he is still unpopular in the Lone Star state. It remains to be seen if he will finish the primary with more potentially embarrassing results.