Pennsylvania Gov. Tom Corbett's approval ratings have gone from bad to worse and are sinking even lower among members of his own party, a new Public Policy Polling poll shows.

In the poll released Tuesday, the Republican governor clings to a 24 percent approval rating while 65 percent of the state disapproves of his performance. Among members of his own party, only 37 percent approve of his performance.

Democrats hold sizable leads over Corbett among the seven candidates polled, including a 20-point margin for Jack Wagner, a 19-point lead for John Hanger and a 15-point lead for Democratic front-runner Allyson Schwartz.

"There's not much doubt Republicans would be better off with a different candidate," the poll notes.

Corbett launched his re-election bid this month with a 12-stop, 7-day swing across the state under the slogan "Promises Kept." But that tour has done little to re-energize a Pennsylvania Republican base that believes there's someone better for governor. According to the poll, 42 percent say they support Corbett as the GOP nominee, but 47 percent say they'd prefer someone else.

It remains unclear who Corbett will face in next year's election, but Schwartz, an incumbent congresswoman, is the early front-runner, with a 21-percent-to-17-percent lead over Jack Wagner. Among those polled, however, 27 percent of voters remain unsure who they'll vote for in the Democratic primary.