Former President Barack Obama traveled to Pittsburgh on Thursday to urge voters there to choose Vice President Kamala Harris in November, aiming a message at one group in particular: Black men.

The decision voters have between the vice president and former President Donald J. Trump, her Republican opponent, “isn’t a close call,” Mr. Obama said as he visited with a group of campaign volunteers and officials at a field office just ahead of his appearance at a Harris rally. His message was for Black male voters whom he said might not be yet on board with Ms. Harris.

Citing “reports I’m getting from campaigns and communities,” he called out what he said was flagging enthusiasm for Ms. Harris compared with the support he received when he was running for the presidency in 2008.

“You’re coming up with all kinds of reasons and excuses,” Mr. Obama said. “I’ve got a problem with that.

“Part of it makes me think that, well, you just aren’t feeling the idea of having a woman as president, and you’re coming up with other alternatives and other reasons for that,” Mr. Obama continued, adding that the “women in our lives have been getting our backs this entire time.

“When we get in trouble and the system isn’t working for us, they’re the ones out there marching and protesting.”