The danger is that the epic struggle between Democrats Barack Obama and Hillary Clinton over their party's presidential nomination will dominate the news and turn Mr McCain into a side issue.

It is a subject that concerns Mr McCain's advisers, but they believe they will be able to keep sufficient focus on the Arizona senator while at the same time raise some much needed campaign cash and work on bringing the Republican Party together behind him.

'You have to be concerned about it,' said senior McCain adviser Charlie Black. 'But I think the answer is we have to go out and make news.'

Mr McCain told reporters in Florida 'it's going to be more difficult obviously' to maintain national visibility 'but at the same time it does give me an opportunity to go around and shore up our base of support, unite our party and energise our party'.

He is expected to give two or three significant speeches over the next couple of months outlining his views on national security, the United States economy and health care.

He will also use many opportunities to contrast his own views with the Democrats, and at some point farther down the road he will go through the process of picking a vice presidential running mate.

Now that Mr Bush has endorsed Mr McCain, his campaign team will work with the Republican National Committee to use its huge fund-raising and message machine to help Mr McCain.

And Republicans feel that Democratic bickering between themselves is not such a bad thing for Mr McCain.

'If we have time breaking into the news coverage it's because the two of them (Obama and Clinton) are fighting like the dickens, spending all that money. So it's a good trade-off,' said Mr Black.

Democrats are already trying to frame the debate about Mr McCain, describing him as a Republican in the same mould as the unpopular President George W. Bush.

'John McCain has worked hard over the last eight years to throw away his maverick image and morph into the ultimate Bush Republican,' said Karen Finney, spokesman for the Democratic National Committee.

A Washington Post-ABC News poll published on Thursday said Mr McCain would lose to either Mr Obama or Mrs Clinton in a hypothetical matchup, but Republican strategists believe he has time to catch up as Democrats fight it out.

'He can come across as the sensible alternative to these people,' said Mr Rich Galen, a Republican strategist who advised the Republican campaign of former Tennessee Senator Fred Thompson.

He said Mr McCain can generate headlines by doing some Senate work.

Mr Trent Duffy, a former deputy White House press secretary, said Mr McCain now has time to reintroduce himself to Americans.

Mr McCain was a Navy pilot shot down in Vietnam and spent 5 1/2 years as a Vietnam prisoner of war.

'People know what the media have told them. Now he has the luxury to define himself and tell people what they don't know about John McCain,' said Mr Duffy.

Mr Karl Rove, who was the architect of Mr Bush's two presidential election victories, wrote in The Wall Street Journal on Thursday that Mr McCain needs to define his views on the Iraq war and the struggle against Islamic extremists in a way that causes Mr Obama and Mrs Clinton to attack him.

'In politics as in war, the properly prepared counterpunch is often more powerful than the assault itself,' he said. -- REUTERS