WASHINGTON — President Obama has a 15 point lead over Mitt Romney in Minnesota, according to a survey of voters released Thursday by Public Policy Polling.

Obama leads the presumptive Republican nominee 54-39, according to PPP. The results are similar to a May poll from SurveyUSA.

Neither of Minnesota’s two former Republican presidential candidates, Tim Pawlenty and Michele Bachmann, would have a dramatic effect on the numbers if added to Romney’s ticket: with Pawlenty as the vice presidential nominee, Obama leads 52-41; Obama’s lead grows to 56-35 if he chose Bachmann.

Both Pawlenty (37-52) and Bachmann (33-60) have net negative favorability ratings in the state, according to the poll. Obama, meanwhile, has a 52 percent approval rating.

The polling firm predicted the race in Minnesota to tighten as November 6 gets closer, but not to the point where it would become a battleground state, which is conventional wisdom among political analysts. The Obama campaign itself has rated Minnesota a “lean Democratic” state.

Devin Henry can be reached at dhenry@minnpost.com. Follow him on Twitter: @dhenry