Can Mitt Romney win the presidential election on Tuesday? The answer is yes, he can — but it’ll be tough. Although the national polls taken in isolation suggest the race is roughly tied, the state-level polling points to a much bigger lead for Barack Obama. It seems that either the national polls are underestimating Obama’s strength or the state polls are overestimating it, or both. Nate Silver’s Fivethirtyeight model  assumes it’s both, so adjusts the national polling slightly towards Obama and the state polls slightly away from him, so they meet in the middle. And that leads it to forecast a win for Obama of slightly more than two points. That sort of margin would more or less guarantee the President re-election.

Romney’s hope, then, is that the state polls are heavily overestimating the President’s support, and that the race is pretty much tied as the national polls suggest. To be clear, there’s no more reason to believe this than to believe that the national polls are heavily underestimating Obama and he’s actually leading by more like four points. But even granting Romney a tie, his route to a majority in the electoral college (270 of the 538 electoral votes) would still be tricky. Back in September, I identified the nine states that looked competitive. Since then, neither campaign has really succeeded in expanding the map — Obama still has 237 ‘safe’ electoral votes to Romney’s 191. So the map looks like this (which I put together at 270towin.com), with Obama’s safe states in blue, Romney’s in red and the nine swing states unshaded:

Of the competitive states, Romney is the clear favourite in just one: North Carolina. He leads by around two points in the polls there, so would almost certainly carry the state if he tied or won the popular vote. So we’ll put the Tar Heel State’s 15 electoral votes in Romney’s column to bring his total up to 206.

Next up is Florida, where the polls show the two candidates exactly tied. Without Florida, Romney would have no chance of reaching 270 — he’d have to win all eight of the other swing states, which isn’t going to happen on the same night he loses Florida. So let’s give Romney the Sunshine State’s 29 electoral votes — he’s now on 235, 35 to go — and move on.

We now come to two states — Colorado and Virginia — in which Obama leads by between one and two points — in other words, enough to make him the favourite, but less than his lead in the popular vote. If the popular vote does end up tied, then, Romney might be the favourite in these states. We’ll therefore grant him their combined 22 electoral votes, brining his total up to 257. That leaves Romney 13 electoral votes short of 270, with five swing states remaining:

Romney’s shortest route to victory from here is winning Ohio. The Buckeye State’s 18 electoral votes would take him over the top, with 275 in total. Unfortunately for Romney, he trails Obama by three points in the polls of Ohio, and there have been so many there that we can be fairly confident of Obama’s lead. In fact, there have been 15 polls of Ohio in the past week alone, and Obama has lead in 12 of them (one shows the race tied, and the last two show slight leads for Romney). Even if we assume that the polls are overestimating Obama’s lead by a couple of points, he’d still be the favourite in Ohio.

And what about without Ohio? Romney could win by taking Wisconsin plus any one of the other three states (Iowa, Nevada or New Hampshire). The trouble is that Wisconsin — which seemed like it might be close after Romney picked one of the state’s Representatives, Paul Ryan, as his running mate — now looks pretty much safe for Obama. The President now leads by about five points in the polling average for the Badger State, meaning it’s tenuous to claim that Romney’s even competitive there anymore.

Without Ohio or Wisconsin, Romney’s only chance would be to win all of Iowa, Nevada and New Hampshire — a very big ask. He’s behind by about three points in Iowa and New Hampshire, and by four in Nevada.

(Incidentally, if Romney took Iowa and Nevada but Obama won New Hampshire, they would have 269 electoral votes each — a tie. That would mean the House of Representatives would pick the President and the Senate would pick the Vice President. Since the Republicans are almost certain to control the majority of state delegations in the House but the Democrats are almost certain to control the Senate, that would probably mean President Romney and Vice President Joe Biden. The chances of a tie are very slim though — about 1-in-500.)

So even assuming a popular vote tie — already a very optimistic assumption for Romney — Obama would still be the favourite to win in each of Ohio, Wisconsin, Iowa, Nevada and New Hampshire, and hence the favourite to win the electoral college. The Romney campaign would like people to think they also have a chance in Michigan, Minnesota and Pennsylvania. That would give them plenty more routes to 270, but unfortunately the polls don’t bear that out: Romney trails by more than five points in Pennsylvania, and by seven in Michigan and Minnesota.

All of this is why, though this election is indeed a close one by historical standards (Silver’s forecast of a 2.2-point margin for Obama is slightly less than the 2.5-point margin George W Bush won by in 2004, but slightly more than the 2.1-point margin Jimmy Carter won by in 1976), it is wrong to talk of the outcome as a ‘tossup’. That suggests Romney’s chances of pulling off an electoral college win on Tuesday are roughly 1-in-2, whereas they’re actually only about 1-in-6.

In fact the most likely single outcome of the election is the map below, in which Obama wins all of the swing states bar North Carolina to give him 332 electoral votes. And this specific combination of states is actually more likely than any combination that gives victory to Romney.

Tags: Mitt Romney, US politics