From the Rasmussen web site: United States Senator John Cornyn has opened a seventeen percentage point lead in his bid for re-election. The latest Rasmussen Reports telephone survey in the state find Cornyn leading Democratic state legislator Rick Noriega 52% to 35%. That’s a significant improvement for the incumbent from a month ago when his lead dwindled to four percentage points. Cornyn is supported by 86% of Republicans and has a two-to-one edge among unaffiliated voters. Last month, his lead among the unaffiliateds was just four percentage points. Noreiga attracts 72% of Democrats, down from 81% a month ago. The Democrat leads among voters under 30, reflecting a nationwide trend. He is competitive among those who earn less than $40,000 a year. However, Cornyn has the advantage among adults over 30 and those with annual incomes topping $40,000. Incumbents who poll below 50% are generally considered vulnerable. Cornyn has moved slightly above that threshold, but many of his colleagues remain in challenging races. At least ten Republican Senate seats are potentially in play for Democrats including seats in Alaska, New Hampshire, North Carolina, Oregon, New Mexico, Colorado, Mississippi, Minnesota, Virginia, and Kentucky. So far, just two Democratic incumbents are polling below 50%–Mary Landrieu in Louisiana and Frank Lautenberg in New Jersey. In Texas, Cornyn is viewed favorably by 56% of the state’s likely voters, up six points from a month ago. He is viewed unfavorably by 31%. Noreiga earns positive reviews from 43% and negative assessments from 39%. Those figures are little changed. Texas voters don’t have firm opinions of either candidate, suggesting limited knowledge of who these men really are. Just 16% have a Very Favorable opinion of the incumbent and 14% have a Very Unfavorable view. Eleven percent (11%) have a Very Favorable opinion of Noreiga while 17% have a Very Unfavorable opinion. Thirty-four percent (34%) of voters say the state’s Republican Governor, Rick Perry, is doing a good or excellent job. Twenty-seven percent (27%) say he is doing a poor job. Those figures have changed little. Forty percent (40%) say President George W. Bush is doing a good or an excellent job while another 40% rate his performance as poor. This poll is in line with one released recently by Austin-based Republican pollster Mike Baselice (Cornyn 49%, Noriega 33%). Baselice is not Cornyn’s pollster. The huge swing compared to Rasmussen’s previous poll, when Cornyn’s margin was just four points raises serious questions about the credibility of the previous Rasmussen poll. These latest figures reflect Baselice’s numbers for the presidential race in Texas, in which John McCain’s lead over Bararck Obama was virtually identical to Cornyn’s lead in the new Rasmussen poll. Since the only thing that has happened since the first Rasmussen poll is that Obama has sewed up the Democratic presidential nomination, the Rasmussen results may simply reflect party identification in the presidential race. I should point out that Rasmussen uses recorded questions to which respondents reply by pressing their telephone keypads. This methodology is also used by SurveyUSA. It has had its successes, notably in the 2004 presidential campaign, but it remains controversial in the polling industry. Huge swings of the sort reflected in the two Rasmussen polls also appeared in SurveyUSA’s monthly tracking polls, when there were no events that could explain the swings.