Will Democrats decide the result of Michigan’s Republican primary?

Tonight’s another very important night for the Republican presidential hopefuls, with primaries in Arizona and Michigan. Mitt Romney seems assured of a decent win in the former, where the latest two polls put him 16-17 points ahead of Rick Santorum. But Michigan is looking incredibly close — with the poll results of the last two days ranging from a four-point lead for Romney to a five-point lead for Santorum.

It could go either way: Nate Silver’s model gives Romney a 55 per cent chance of victory to Santorum’s 45 per cent chance. With the polls this narrow, it will all come down to who’s best at getting their voters out — and even that is tough to predict here. Romney has the better organisation on the ground, but Santorum’s voters seem, in general, to be more enthusiastic. It is worth remembering that Santorum beat the poll-based predictions in Iowa, South Carolina and — by a long way — in the three states that voted three weeks ago.

And there’s one group of voters who could put Santorum over the top: Democrats. Michigan’s primary is ‘open’, which means that you don’t have to be a registered Republican cast a vote, as you do in some of the other states.

In 2008, such ‘open primaries’ saw many Republicans crossover to vote for Obama because they thought he’d make a better President than any of the Republican field. This time, Democrats are hoping to exploit this by getting their supporters to turn out for Santorum — not because they want him to be President, but because they think he’ll make an easier opponent for Obama if he wins, and leave Romney weakened even if he doesn’t. And Santorum’s also trying to appeal to the Democrat vote himself, although he says they should support him ‘to send a loud message to Massachusetts Mitt Romney’ rather than ‘to make things easier for Barack Obama’.

Romney, naturally, isn’t a fan of Santorum’s strategy. He’s called them ‘outrageous and disgusting, a terrible dirty trick’ and said ‘we don’t want Democrats deciding who our nominee’s going to be, we want Republicans deciding who our nominees are going to be’. He also described it as ‘a new low for his campaign and that’s saying something’.

But there’s nothing new about the Democrats’ tactics. In 2008, conservative talk show host Rush Limbaugh asked Republicans to ‘pimp yourselves for a day’ and vote for Hillary Clinton ‘to keep this campaign going, this Uncivil War’ because ‘We want the Clinton campaign to keep pumping out these pictures of Obama dressed up as Bin Laden. We want this kind of stuff.’ And, it turns out, one Willard Mitt Romney voted in the 1992 Democratic Primary for the same reason. As he said in 2008:

‘When there was no real contest in the Republican primary, I’d vote in the Democrat primary, vote for the person who I thought would be the weakest opponent for the Republican.’