Primary Election Day in Pennsylvania isn't until May 18, but Rasmussen Reports says Attorney General Tom Corbett, a Republican, and Allegheny County Executive Dan Onorato, a Democrat, will likely emerge as their respective party nominees.

From Rasmussen Reports:

State Attorney General Tom Corbett earns nearly 50% support again this month in Pennsylvania's race for governor, while only one of his Democratic opponents seems to be gaining any traction.

The latest Rasmussen Reports telephone survey of likely voters in the Keystone State finds Corbett with 45% to 49% of the vote depending on his opponent, but this marks no change from last month. In February, his best showing to date, the Republican picked up over 50% support in two of the three match-ups.

Allegheny County Chief Executive Dan Onorato is the one Democrat who appears to be gaining some ground. Corbett now gets 45% of the vote to Onorato's 36%. Eight percent (8%) like another candidate, and 11% are undecided. A month ago, Corbett led Onorato 46% to 29%, but he posted a two-to-one lead – 52% to 26% - over the Democrat in February.

Corbett holds a 49% to 29% lead over former Congressman Joe Hoeffel, who, according to the Philadelphia Inquirer, views himself as the only true liberal among the Democratic candidates. Given this match-up, 11% prefer some other candidate, and 11% more are undecided. This race is virtually unchanged over the past two surveys.

The Republican picks up 48% support if State Auditor Jack Wagner is his Democratic opponent. Wagner earns 27% of the vote, a six-point drop from last month when he was Corbett's strongest foe. Eleven percent (11%) favor another candidate. Fourteen percent (14%) are undecided. But in February, Corbett led Wagner 49% to 28%.

Read more about the poll at Rasmussen Reports.