The race for retiring Democratic Assemblyman Bob Reilly‘s seat is getting more crowded by the day. The latest contestant to mull throwing his hat into the ring is Reilly’s chief of staff, Tim Nichols.

Nichols, who does double duty as an Albany County legislator, confirmed last night that he is mulling a run, even though his boss has already endorsed a successor – Assembly Majority Leader Ron Canestrari’s top aide, Kevin Frazier.

In a brief telephone interview last night, Nichols told me he’s “very seriously considering” a run, and in the meantime still continuing his duties as the assemblyman’s top aide.

“I have not made a decision as to what my plans are, and so I feel an obligation to continue serving in the capacity as chief of staff to help Bob and help people of 109th district,” Nichols said.

“That’s how I see my job right now. We’ll leave it at that.”

Nichols said he’s unconcerned about the changes in the district, which actually was renumbered the 110th from the 109th in the redistricting process.

The bulk of the district will remain the same, with its base in Colonie – long Nichols’ home. The additions in Schenectady and Niskayuna are fine with him, the county legislator said, because he is familiar with the area and has family members there.

Nichols said he expects to make a decision in the next couple of weeks. He would not comment on whether he’ll ask Reilly to reconsider his endorsement of Frazier, saying only: “He made a decision and, you know to be honest, I’m not really prepared to comment on it at this time.”

The TU reports Republican Jennifer Whalen, who lost a close race to Reilly in 2010, is mulling another run now that the seat is open.

Also, Nichols’ county legislative colleague, Phil Steck, is planning to run. So this could end up a three-way Democratic primary before all is said and done.