According to Rasmussen, Cornyn is vulnerable in the upcoming November election..check out what he wrote on his site:

Election 2008: Texas Senate

Texas Senate: Cornyn 47% Noriega 43%

It’s time to add United States Senator John Cornyn to the list of potentially vulnerable Republican incumbents in Election 2008. The latest Rasmussen Reports telephone survey in the state find Cornyn leading Democratic state legislator Rick Noriega by just four percentage points, 47% to 43%.

Any incumbent who polls below 50% is considered potentially vulnerable. That is especially true when a little known challenger is so competitive in an early general election match-up. The race for President in Texas is also fairly competitive early in Election 2008.

Noreiga leads among voters earning less than $40,000 a year. Cornyn leads among those with higher incomes. Cornyn leads among Evangelical Christian voters and other Protestants. Noreiga leads among those with a different faith background. Both candidates do well within their own party and are fairly evenly matched among unaffiliated voters.