TONIGHT Mayor Nutter will put on a nice suit and welcome guests to a $1,000-a-head cocktail party at the Franklin Institute to raise money for his campaign fund, which reported $1.1 million on hand in January. Does he really need to start raising money for his re-election now?

No. It's just something mayors do, even reform mayors.

Having a big war chest allows you to donate to other campaigns and influence other politicians, presumably for the public good.

But allow me to raise a quibble here. In tapping his supporters for a bunch of four-figure contributions, Nutter is benefiting from a flaw in the city's campaign-finance law. This flaw gives incumbents a big advantage over potential rivals.

The 2003 law limits contributions to candidates for city offices, but the limits are applied on an annual basis. That means that Nutter can get his donors to give the maximum this year, and again next year, and again in 2010 and 2011, when he's up for re-election. The limit for, say, a law firm or insurance broker who would like city business is $10,600 a year, so the firm could legally contribute $42,400 in an election cycle.

By the time Nutter runs for re-election, he can accumulate a pretty intimidating stash. Allowing incumbents to tap their contributors to the max every year practically forces potential challengers to start raising money years in advance, giving us a perpetual campaign.

It would be smarter to impose the contribution limits per election, as federal campaign laws do, rather than per year. That would solve another problem with our law.

As things now stand, a candidate who spends heavily on a contested primary isn't able to go back to contributors for fresh donations for the general election, since the general and primary occur in the same year.

That means that somebody who faces a competitive primary is at a huge disadvantage against a rival who had no opposition.

This could have been a big problem for Nutter in the 2007 mayor's race if the Republicans had fielded a strong, well-funded candidate.

I raised these issues in a December column, and the city Board of Ethics soon recommended that Council and the mayor change the law so that contribution limits apply to candidates per election, and not per year.

"The intent of the law is to limit the influence of money over our elected officials, and people are generous to people in power," Ethics Board Executive Director Shane Creamer told me yesterday.

So what's happened since December? Nothing.

When I asked Nutter about the issue last night, he gave me a puzzled look.

He's hosting a fundraiser like elected officials do everywhere, he said, and anybody who wants to start raising money to run against him is free to do the same.

We debated the issue a bit, and he acknowledged that the campaign finance law could use some tweaking.

"We should take a comprehensive look at all our campaign finance laws," Nutter told me. "There are a number of groups we can engage and take our time - and I don't mean forever - and look at what other cities are doing and fix any concerns in our law."

Nutter has certainly earned the benefit of some doubt on this issue.

He didn't just support ethics laws in City Council.

When he decided to run for mayor, Nutter publicly pledged to stick to contribution limits two years before the election, when none of his rivals would, when nobody knew if the city law would survive legal challenges, and when he was up against a millionaire promising to spend $5 million of his own cash on the race.

That took guts, and he deserves all the credit and praise he got for sticking with the limits and winning.

But I don't want him to forget where he came from.

The problem is, there's no particular time or deadline for reforming the campaign finance law, and little interest by a City Council that often seems, as Councilwoman Jannie Blackwell once put it, "ethics-ed out."

So it will take some push from the mayor to get this done, and I have a timetable to suggest: Let's do it before the mayor's next fundraiser. *