The city’s new campaign-finance law kicks in early next year, and insiders say local pols are in a gold rush to get those last big checks from lobbyists. Suri Kasirer, the city’s top-grossing lobbyist last year, says she’s been approached by several in recent weeks who have asked her to contribute the current $4,950 limit for citywide races. Under the new law, championed by Mayor Bloomberg and City Council Speaker Christine Quinn, lobbyists will max out at only $400. “It’s absolutely annoying,” says Councilman Peter Vallone Jr. of the new limit. He netted $200,000 at a fund-raiser at Bloomberg’s townhouse earlier this month and is considering a run for Queens borough president. Lobbyist Sid Davidoff is gathering a consortium of industry leaders to sue the city over the limit before the end of the year; he calls them unconstitutional. Politicos also complain that the law has a major loophole—unions aren’t covered by it. Which could help the labor-friendly Quinn. Since her supporters tend to write smaller checks than do those of her chief competitors for the mayoralty in 2009, she should be less burdened by the new limit. According to records, the average donation Quinn has received is $994 (she has reported $1.4 million in total) while City Comptroller Bill Thompson Jr. has received an average $2,760 per donor (he has $3.2 million) and Congressman Anthony Weiner has received $2,159 per donor (he has $2 million).