It’s a story that won’t go away: the idea that the ALP might again do a preference deal with the Assemblies of God party, Family First, despite the angst that it brought them in 2004. Christian Kerr presented the case for it in yesterday’s Crikey, and unidentified Labor “sources” echo his argument in this morning’s Australian.

As far as the lower house goes, Christian is probably right. Although Family First has fewer votes than the Greens, its preferences may be worth more because its voters are more responsive to direction, and because in the absence of a deal they will almost certainly be directed to the Coalition – which Labor knows the Greens will not do.

But the Senate is a different animal: minor parties there can win seats as well as just influence things with their preferences. And the state of the numbers means it’s of no advantage to Labor to elect Family First senators instead of Greens.

The current Senate has 39 Coalition senators against 28 Labor, four Greens, four Democrats and one Family First. A best-case scenario for Labor is that it picks up the four Democrat seats, plus a Greens seat in NSW and a Liberal seat in Tasmania, and that the Greens win two seats from the Liberals, in Victoria and the ACT.

That would give Labor and the Greens a combined 39 seats, a narrow majority over the 36 Coalition plus one Family First. Giving one of those Greens seats to Family First instead – as happened in Victoria last time, and might again – can only hurt Labor: it would give Family First the power to combine with the Coalition to block Labor’s legislation.

The point is that having more Family First senators wouldn’t give Labor any extra options, because there’s still no way that Labor plus Family First will have a majority. That’s why the analogy with the state upper houses is misleading.

So there are two questions for the ALP. Is the advantage it might get in some marginal Reps seats worth the risk of weakening its position in the Senate? And is any short-term electoral advantage worth the long-term price of building up a new force on the religious right?