U.S. Sen. Ted Cruz has a negative net approval rating according to a new poll (PDF) from Raleigh-N. Car.-based Public Policy Polling. Thirty-nine percent of respondents approve Cruz’s job performance in the Senate and 48% disapprove.

Half of self-identified “Republican primary voters” would prefer Cruz be the party’s 2018 senatorial nominee, and 43% would prefer “someone else.” Former Gov. Rick Perry polls slightly ahead of Cruz, 46%-37%, in a hypothetical race, but Cruz is more than 20 points ahead of U.S. Rep. Michael McCaul (51%-19%) and Lt. Gov. Dan Patrick (49%-27%).

Anticipating the general election, Cruz wins hypothetical races against U.S. Housing and Urban Development Sec. Julian Castro, 48%-36%, and former Sen. Wendy Davis, 49%-37%. Gov. Greg Abbott is far ahead of Castro, 57%-28%, and Davis, 57%-32%, in hypothetical re-election races.

Two thirds of “very conservative” voters approve of Cruz’s job performance in the Senate, and 72% of those voters would like to see Cruz as the party’s senatorial nominee in 2018. Among those voters, Cruz leads Patrick, 66%-18%, and McCaul, 64%-14%. Cruz also leads Perry, 48%-42%, among “very conservative” voters even though 83% of them view Perry favorably versus 67% for Cruz.

Polls taken more than a year prior to an election must be taken with particularly large grains of salt. Consider a PPP poll from February 2009 (PDF) showing then-U.S. Sen. Kay Bailey Hutchison with a 25-point lead over then-Gov. Perry among “voters likely to vote in the Republican primary.” Hutchison “leads with every subgroup of the population PPP tracks,” leading PPP to conclude “Perry is going to have an uphill climb to keep his seat.” A year later, Perry defeated Hutchison, 51%-30% (Tea Party pioneer Debra Medina received the other 19%.).