It’s mayoral candidates 2, Sanitation Department 0 in the million-dollar battle over illegal campaign posters.

Bill Thompson became the second major mayoral contender to beat the system last week, when the Environmental Control Board overruled its own hearing officer and tossed $619,125 worth of summonses accumulated during his 2009 run for City Hall.

The board’s decision was based on legal technicalities. It never got to the merits of the case.

The ECB voided 8,225 summonses, saying the sanitation agents who mailed them to Thompson didn’t list the exact number contained in five of nine envelopes.

Earlier, a similar defect led the ECB to dismiss $528,225 worth of fines slapped on Comptroller John Liu’s campaign, also in 2009.

Both men are considered likely to enter the 2013 mayoral contest.

The Sanitation Department was so incensed by the turn of events in Liu’s case — where he dispatched an aide to pick up summonses and then challenged the service as improper — that it re-issued all the violations again.

So Liu will face yet another hearing at the ECB in September.

Thompson’s lawyer, Jerry Goldfeder, cited the Liu decision in his successful appeal.

Sanitation officials had no immediate comment on the ruling involving Thompson.

Another mayoral candidate, Public Advocate Bill de Blasio, is fighting his own poster battle with $303,750 in fines at stake.

READ MORE: NY POST