Republican incumbent: John Cornyn
Democratic candidate: Rick Noriega
Cornyn, 56, has represented Texas in the U.S. Senate since 2002. He earlier served as a judge and as state attorney general in Texas.
Noriega, 50, has served in the state House of Representatives since 1999.
Real Clear Politics lists polls, all of which show Cornyn ahead, but by divergent margins ranging from 2% to 17%.
Here is a Houston Chronicle report from earlier this month, describing Cornyn's approach to the campaign. If Cornyn is indeed as complacent about Noriega's challenge as that article contends, it's not clear that his poll numbers necessarily justify that. However, Noriega does appear to be somewhat of a longshot.
Whether or not one classifies Texas as a "southern" state (Lyndon Johnson liked to call it "western", in part because, when he was developing his presidential ambitions during the 1950s, he didn't think the country was ready to elect a southerner), it has followed the typical pattern of moving from staunchly Democratic to staunchly Republican.
Cornyn's Senate seat has been in Republican hands since John Tower replaced Johnson in 1961. The other Texas seat was last held by a Democrat in 1993, when Bob Krueger held an interim appointment following fellow Democrat Lloyd Bentsen's appointment as secretary of the treasury.