On the heels of the first head-to-head post-primary poll in the Pennsylvania governor's race, The Washington Post still lists Gov. Corbett as the nation's number one incumbent likely not to remain an incumbent.

A Rasmussen Report poll released Sunday shows Corbett trailing Democratic nominee Tom Wolf by 20 points (51-31) with 14 percent undecided.

The poll says likely voters trust Wolf more than Corbett on social issues, ethics and on government spending and taxes. And it says while 83 percent of Democrats back Wolf, just 59 percent of Republicans back Corbett. And Wolf holds a 10-point lead among independents.

Yes, it's early. And, yes, polls in the absence of an actual campaign are notoriously unreliable. But there does appear to be a pattern here.

In a Post ranking of 15 gubernatorial races, Corbett remains at the top of the list of governor's seats most likely to change party control.

Here's what The Post says:

1. Pennsylvania (R): Now that Democrats have completed their messy primary, they can focus on Gov. Tom Corbett (R). Businessman Tom Wolf (D) has deep pockets but has said he's not going to self-fund in the general election. He remains Democrats' best hope for a pickup. (Previous ranking: 1)

The second and third most-endangered incumbents listed are, respectively, Republican Maine Gov. Paul LePage and Republican Florida Gov. Rick Scott.

You can read the full list here.