Over the past few weeks, potential candidates have been dropping out of the race to be the Republican nominee to challenge President Obama in 2012 – and a few even entered, but in truth ite is almost irrelevant whom the GOP selects to carry the party's standard: Obama will almost certainly win, and it seems that the Republicans know it.

However, that's not to say the race is over, or even that it won't be interesting. But for the real movements you have to look below the headline fight of Obama vs the Republican candidate.

The elections for the Senate and the House of Representatives will shape Obama's second term and will be the difference between him being a lame duck and a President that continues with his agenda and has the ability to make real changes. Since the November 2010 midterm elections, the Republicans have controlled the House of Congress and wiped out the supermajority the Democrats enjoyed in the Senate.

This has meant near deadlock on Obama's legislative agenda and almost brought about the shutdown of the federal government over budget negotiations. Depending on the outcome of House and Senate elections next year, it could be four more years of the same stalemate – or it could see Obama making real progress on his agenda, ensuring his healthcare plans are fully implemented and not repealed.

While the Republican primary race will prove interesting, the more telling outcome will be how 2012 shapes the field of candidates – both Democratic and Republican – for 2016. 2016 will be the true horserace: with no incumbent president and the vice-president not running, four years out and it is difficult to see who the Democratic challengers are likely to be. Eight years of a Democrat in the White House leaves space for a capable Republican to stand a real chance. Looking ahead, Republican candidates will be using the campaign this year and next to launch themselves towards the 2016 nomination.

Mike Huckabee, the former state governor-turned-Fox news pundit, has decided not to run, even though he has been growing a significant base of supporters among Republicans since he came second to John McCain in 2008. Donald Trump, the Lord Sugar of the American Apprentice and populist (if not popular) businessman, has also decided against running after appearing seriously to be considering entering the race, and even pseudo-campaigning for a while.

Haley Barbour, another highly rated governor, also announced that he will not be throwing his hat in the ring – despite building up a campaign team and visiting the early primary states.

Paling attraction

Sarah Palin, perhaps the best-known name in the Republican field, is yet to announce her intentions, but may follow in the footsteps of Huckabee and Trump. Speculation suggests that she is enjoying life outside elected office enough to be relucant to seek out the rigours of a tough campaign unlikely to end in victory.

Newt Gingrich, the former speaker of the House, celebrated for initiating the impeachment hearings against Bill Clinton, has had a poor start since making his announcement. He has been a player in the political field for a long time now, and may not represent the "fresh face" that Republicans will undoubtedly look for. His extramarital affairs won't help among the staunchly conservative Republican base voting in the primaries.

That leaves Tim Pawlenty, Jon Huntsman, Michele Bachmann and Mitt Romney. Romney, the former governor of Massachusetts and businessman, is many people's favourite to win the GOP nomination. The fact that he raised $10m in one day last week is a good example of why.

Do Pawlenty and Huntsman also want him to win? Both are credible candidates: Pawlenty a successful and popular governor in Minnesota; Hunstman a former CEO, governor of Utah and President Obama's ambassador to China for two years. However, neither is particularly well known nationwide (59 per cent of Americans felt neither favourable nor unfavourable towards Pawlenty in Ipsos's March poll) and while that didn't stop Obama in 2008, this is a very different election.

These two relatively young candidates will use this election cycle to build their national profile and grow support bases in the key states. Their next four years will be just as important. They will need to keep whatever momentum they gain this time around. Four years ago, Huckabee was an unknown, but he's now a recognisable face to many and, had he decided to run, he would have been in a very strong position to win the Republican nomination.

View to a killing

Our latest research shows Obama leading all his opponents, which is hardly surprising at this stage. Although the polls also show a small bump for Obama since the killing of Osama Bin Laden, it is unlikely to make much difference in the long run. It does however strengthen his personal position and closes off an avenue of attack from the Republicans.

They will find it far more difficult to accuse him of being weak on terrorism or defence – three in five Americans (59 per cent) give Obama a satisfactory rating on terrorism, up from 43 per cent before the death of Bin Laden.

Obama's electoral fortunes – as those of David Cameron and the Conservatives in Britain – lie in the success or failure of the economy. The most likely obstacle that could prevent Obama staying in the White House would be an economic downturn and increasing unemployment. Current projections suggest this won't happen, but the Republicans could do worse than learn from a little-known governor of Arkansas in 1992.

No one gave Bill Clinton a chance against the incumbent, President George H W Bush, but with the economy sliding and the independent Ross Perot splitting the vote, he forged a victory. You've got to be in it to win it.

Another Democrat provides a warning story for those Republicans looking ahead to 2016. John Edwards believed that coming second to John Kerry in 2004 and becoming Kerry's running mate made him a shoe-in for the 2008 nomination, before the junior senator from Chicago, Barack Obama, stole his momentum.

A repeat of 1992 is unlikely. The Democrats need to concentrate on winning key House and Senate races in order to give the president at least two years in which he can pass the legislation he wants. The Republicans are playing a risky game if they're looking ahead to 2016. However unlikely, every election is winnable and Republican candidates for House and Senate seats will be grateful for a presidential contender who gets the Republican vote out.

Tom Mludzinski is a research executive at Ipsos MORI, the social research institute.