While Mr. Cornyn is leading most polls, his numbers have been extremely low. 40% is atrocious for an incumbent who has been in office since 2002 and won with 61% of the vote last time. Pure tossup.
Agreed. And Cornyn only won by that much in 2014 because it was an
extremely low turnout election, his Democratic opponent that year (David Alameel) was a complete unknown and barely campaigned, and it was a Republican wave year in Texas and elsewhere (that was the same year Wendy Davis, who is now within reach of a House seat, was crushed by Gregg Abbott, which undoubtedly helped Cornyn). In 2008, Cornyn "only" beat Rick Noriega 54-42%, underperforming John McCain, and in 2002, he won over Ron Kirk 55-43%, again underperforming George W. Bush in both of his elections and Texas' other Senator, Cruz's predecessor Kay Bailey Hutchison (who always got more than 60% of the vote in her elections). So Cornyn has never been an electoral titan, and it's no surprise that he's only running even with the state's current lean, as it's become more Democratic.