WASHINGTON – An open South Jersey House seat has presented an enticing opportunity for candidates there: the chance to hit up donors for twice as much campaign money without having to do any extra campaigning.

Instead of being limited to giving the nomral maximum of $5,200 this year, donors can give up to $10,400 to each candidate running to replace former U.S. Rep. Rob Andrews, a Democrat who resigned in February. Political Action Committees can give up to $20,000 to each candidate, instead of the normal $10,000 limit.

Here's why: technically there are four elections to replace Andrews – two on the June 3 primary day, and two on the Nov. 4 general election -- not just the usual one on each day. So donors can give the maximum campaign contribution four times, instead of twice, even though the candidates don't have to worry about any added days of voting.

It's perfectly legal, and there's more on the reasoning below. For now, Democratic state Sen. Donald Norcross is already taking advantage. His brother, political power broker George Norcross, sent out a fund-raising invitation Monday morning seeking donations of up to $10,400 per individual or business partnership, and up to $20,000 per PAC for a March 25 fundraiser at Auletto Caterers in Deptford. (George Norcross is also managing partner of the company that publishes the Inquirer and Philly.com).

Republicans haven't settled on a candidate yet, but whenever they do, he or she will also be able to take advantage of the higher campaign limits, as will any other primary contenders who have deep-pocketed donors. Ex-Eagle Garry Cobb has said he intends to run as a Republican, but has not made his candidacy official.

The district is heavily Democratic and has not been competitive in decades, so Norcross may not need a huge sum of money. But the larger war chest he (or any eventual winner) builds, the more the new member of Congress can have on hand to distribute to his or her colleagues, a good way to make new friends on Capitol Hill.

This is how the donation limits work, and why they're doubled for this race: normally individual donors can give up to $2,600 per election – so a total of $5,200 per cycle ($2,600 in the primary election and $2,600 in the general).

But Andrews' resignation has set the stage for four elections: a primary and a general to fill the rest of his term (all two months of it once the November election rolls around to pick his replacement), and a primary and a general for the new two-year term that begins in January. Both primaries will be on June 3 and both generals on Nov. 4. Voters in the district will vote twice each day.

But from the candidates' perspective, it's hard to imagine them needing to do any extra campaigning, advertising or launching any added get-out-the-vote operation. Like nearly everyone else up for election this year – and bound by the normal donation limits -- they still only have to worry about two days of voting.

To be clear, the extra donations are allowed. Federal Election Commission rules say these are separate elections, even if they happen on the same day. So Norcross' fund-raising invite specifically seeks $2,600 for the unexpired term primary, $2,600 for the full-term primary, $2,600 for the unexpired term general election and $2,600 for the full-term general election.

"If there are multiple elections, candidates may raise separate contributions up to the $2,600 maximum for each," wrote FEC spokeswoman Judith Ingram.

Sen. Cory Booker (D., N.J.) went through a similar process last year: he tapped his top donors for twice the normal limit because he was running to fill an unexpired term in 2013 and a full Senate term in 2014. But he at least faced the prospect of four different election days to campaign for: a primary and general each year.

Norcross and anyone else who jumps in the South Jersey race only have to draw voters out twice – but they'll be able to collect twice as much campaign money as normal to do so.

You can follow Tamari on Twitter or email him at jtamari@phillynews.com.