Plastic bags, bike-sharing programs, and Philadelphia City Council powers have not been big issues thus far in this year's mayoral race, but Tuesday night, they offered unexpected opportunities for candidates to stand apart.

Those opportunities, along with some rather quirky personal questions, enlivened a mayoral forum at the Convention Center held by the Next Great City Coalition, a broad collection of unions, community groups, businesses, churches, and nonprofits.

The forum drew candidates Lynne M. Abraham, Nelson Diaz, the Rev. Keith Goodman, James F. Kenney, Doug Oliver, and State Sen. Anthony Hardy Williams.

The six Democrats were asked to consider an array of issues near and dear to Next Great City members, including the need for free drinking water and nutritious food for all of Philadelphia's school students, fewer restrictions on small businesses, more trail and bicycle-lane access, and cleaner public spaces.

Subtle and not-so-subtle differences began to show when the group was asked to considered the value of tax abatements. There was a consensus that Center City had sufficiently benefited from the current 10-year abatement program for new construction. And all thought it should be expanded to struggling neighborhoods citywide. Oliver, however, broke ranks and said it was worth considering ending the practice in Center City.

The question of requiring small deposits on plastic bags to reduce litter also revealed some fault lines.

Oliver, Abraham, Kenney, and Diaz all gave the idea two thumbs up. Then Williams spoke. "No. It is a regressive tax" on the people who can least afford it, the city's have-nots.

He said education was a better way to fight litter in neighborhoods. He leaned on a proposal he made earlier in the evening - restore weekly street cleaning citywide. That proposal received a rousing cheer.

Goodman seconded Williams' opposition to a plastic bag deposit for the same reason.

That concern for the have-nots also influenced the positions of Goodman and Williams when it came to the discussion of bike lanes and bike-sharing programs.

While the other candidates spoke largely of wanting to expand the number of bike lanes, Goodman and Williams expressed concern that the coming bike-share program would prove too expensive for the city's poorest residents, who might be the most in need of such transportation.

And there was the question of whether mayoral appointments should have Council approval.

Abraham, Diaz, Goodman, and Kenney - a former councilman - were all opposed to such an expansion of Council power. Oliver was fine with it. Williams suggested there might be a middle ground that allowed for Council hearings to vet candidates.

Finally, there were some offbeat questions just to mix it up.

Who is your favorite mayor?

Abraham: Richardson Dilworth. Kenney: Ed Rendell. Oliver: W. Wilson Goode. Diaz: Dilworth and Rendell. Williams: Rendell. Goodman: John F. Street.

And something surprising about yourself?

We learned that Abraham likes to cook, Diaz's wife has fought for the rights of abused women, Williams is a loving grandfather, Goodman plays the piano, Kenney reads poetry, and Oliver, at age 40, has had two hip replacements.

There you go.