WINNER: Republican presidential nominee Mitt Romney received a boost in opinion polls after a strong performance in the first presidential debate.

Politics is a competitive process. Candidates who try to place themselves above the fray often find themselves driven below the fray.

The first of three presidential debates in Denver last week underlined this lesson and served as a wake-up call for President Barack Obama's campaign.

Doubtless, the Democrat team advising Obama reminded him on the eve of the debate that he was leading the Republican contender, Mitt Romney, in the polls, and that there was no need to risk looking less presidential by slugging it with his gaffe-prone political rival. But the strategy clearly backfired.

The eager Mitt Romney had one of his strongest debate performances while a subdued Barack Obama turned in one of his worst.

Romney came across as quicker, more organised, focused and more audacious than President Obama on October 3.

Obama, given numerous opportunities to counterattack some of Romney's points and claims, appeared reluctant to do so and instead settled for a defensive and wordy contribution to the debate.

Polls taken since the first presidential debate show a tightening race.

A Reuters/Ipsos online tracking poll released on Friday has Romney drawing four points closer to Obama than he had been just before the debate just two points behind now at 44-46.

During the debate and in the period since, Romney, who declared himself "severely conservative" during the Republican primaries, has tried to reposition himself as a centrist.

This is evident in three key areas.

First, on the economic front, Romney seems to be backing away from his much-touted plans for cutting income tax rates by 20 per cent for people at all income levels, and repealing the 2010 Wall Street and banking regulations which purportedly stifle economic growth.

Second, Romney is playing up the health care programme that was his signature accomplishment as governor of Massachusetts and would return health policy to the states by scrapping Obama's health law, known as Obamacare.

Third, Romney aspires to spend $US2 trillion ($NZ2.4 trillion) more on defence over the next 10 years to make America strong again and meet what he calls "a longing for American leadership" in the Middle East and elsewhere.

But Romney's new-found moderation will surely now be put to the test by President Obama in the next two presidential debates and in the weeks ahead on the campaign trail.

Buoyed by a record fundraising effort of $181 million for the month of September and boosted by the September jobs figures that showed unemployment dipped from 8.1 per cent to 7.8 per cent, Obama will be going all out to regain the initiative in the presidential race.

The tempo of the campaign will almost certainly escalate this week as the Obama camp will seek to vigorously sell the president's track record in office and target vulnerabilities in the Romney challenge.

Among other things, President Obama will seek to remind Americans that he inherited from George W. Bush's Republican administration the worst financial crisis since the late 1920s and two wars, in Iraq and Afghanistan.

Since October 2009 unemployment has fallen from a peak of 10 per cent and the economy has had more than 30 weeks of continuous but modest growth.

At the same time, Obama has ended the US combat role in Iraq, masterminded the elimination of America's No 1 enemy, Osama bin Laden, and begun the process of disengaging from the war in Afghanistan.

In addition, Romney can expect relentless scrutiny from the Obama camp over the precise status of his tax cut plan.

The nonpartisan Tax Policy Centre has estimated that Romney's tax cuts would cost nearly $5 trillion.

Romney disputes this claim. But he will now be under strong pressure to either confirm he has ditched the plan altogether or admit he has retained the plan in a modified form.

He will also be pressed over his plans to scrap Obamacare - which extended health care to more than 40 million Americans previously without health cover - and can also expect spirited demands on how he is going to pay for the huge investment he plans for the Pentagon.

Americans, as Obama pointed out recently, have fresh memories of wars being fought on the credit card and know that it contributed to the conditions that led to the 2008-09 Wall Street crash.

Meanwhile, Romney will certainly be probed about how he can assert "strong" American leadership in the Middle East and elsewhere without repeating the disastrous unilateralism of the George W. Bush leadership era.

Unless Romney can come up with some pretty convincing responses to the growing Obama counteroffensive after the first debate, he may yet find many Americans unwilling to switch horses in the middle of the stream.

• Robert G. Patman is Professor of International Relations in the Department of Politics, University of Otago.