With the country split along partisan fault lines and the presidential election in November expected to be extremely close, neither Bush nor the presumed Democratic nominee John Kerry can afford any significant defections from their base support.
While Kerry must contend with the prospect of losing a small percentage of left-wing liberals to Independent candidate Ralph Nader, Bush is fighting to ensure that recent poll ratings do not translate into a diminution of support from the margins of the Republican Party.
According to a recent poll, roughly 20% of Republican voters remain uncommitted to Bush, something that could prove costly to the president in a close race, says conservative pundit Robert Novak.
In a 20 May column for the Chicago Sun-Times, Novak wrote that the poll, along with a lack of public support for Bush from key Republican figures, could indicate some looming problems for Bush.
"Actually, when nearly one out of five Republicans cannot flatly say they support Bush, that could spell defeat in a closely contested election," Novak wrote.
"Actually, when nearly one out of five Republicans cannot flatly say they support Bush, that could spell defeat in a closely contested election"
Despite Bush's enormous popularity in the conservative establishment, not everyone is pleased with his performance, says Nathan Gonzales, political editor of The Rothenberg Political Report.
"There is grumbling in certain factions of the Republican Party," Gonzales says. "When things are not going well, everyone has a solution."
But it would be far too early to draw conclusions as to the president's standing among conservative voters, he says.
Many undecided Republicans will probably "come home" as the election draws closer.
"The alternative is John Kerry and I doubt at this point that there are many Republicans who are so disenchanted with Bush that they would vote for Kerry," he says.
Still, the election could tilt on Bush's ability to sway moderate conservative voters.
"If [Bush] only gets 80% [of Republican votes] on election day that could be a problem," Gonzales says.
Much of the scrutiny centres on US operations in Iraq, where the recent prisoner abuse scandal sparked a dip in public support for Bush's handling of the occupation.
In a recent CBS News survey, only 30% of those polled said Bush was doing a good job of managing Iraq.
In the past several weeks, a few key Republican members of Congress have expressed indirect criticism of the administration's Iraq policy.
Chaos in Iraq is hurting Bush's
In a 3 May speech at Kansas State University, Republican Senator Pat Roberts took a shot at the neoconservative-inspired plan to use Iraq as a starting point for democratisation of the Middle East.
"It seems to me that in fighting the global war against terrorism, we need to restrain what are growing US messianic instincts - a sort of global social engineering where the United States feels it is both entitled and obligated to promote democracy, by force if necessary," Roberts said.
The senator also called for more accountability from the administration for its apparent intelligence failures leading up to the war, an opinion shared by a growing number of conservatives, Novak says.
"These are precisely the concerns I have heard all over the country from people who call themselves Republicans and are distraught about the US adventure in Iraq," Novak wrote in a 13 May column in The Washington Post.
The feeling among many Democrats that the Bush administration has been too obstinate in refusing to acknowledge mistakes or consider a major course reversal in Iraq is beginning to take hold among some prominent Republicans.
"This administration cannot be trusted to govern if it cannot be counted on to think and, having thought, to have second thoughts," conservative pundit George Will wrote in a recent Washington Post editorial.Republican dissenters
While the criticism coming from Novak and Will do not necessarily represent the views of Republican voters across the country, these are voices the conservative establishment listens to, Gonzales says.
"It is important that [Bush] eventually get those people on board, because these are columnists that Republicans read day in and day out," he says.
"Even those who have been stalwart supporters of the president's decision to invade Iraq now have many questions about how we make the transition to a peaceful and democratic country"
The president must also convince members of his own party in Congress that he has a plan for success, Republican Senator Susan Collins told The New York Times.
"Even those who have been stalwart supporters of the president's decision to invade Iraq now have many questions about how we make the transition to a peaceful and democratic country," Collins said.
In a recent address, Bush tried to turn the tide of public opinion back in the administration's favour.
He offered a five-point plan and emphasised the role the United Nations would play in the transfer of sovereignty to an Iraqi interim government.
Bush also sought to underscore his commitment to Iraq in the face of ongoing violence directed at US troops.
"There are difficult days ahead and the way forward may sometimes appear chaotic," Bush said. "Yet, our coalition is strong. Our efforts are focused and unrelenting and no power of the enemy will stop Iraq's progress."
Iraq, however, is not the only source of concern among traditional conservatives, many of whom are upset about domestic spending issues related to the ballooning federal deficit.
"Federal domestic spending is out of control," David Keene, chairman of the American Conservative Union, wrote in a recent letter to members.
Will traditional Republicans vote
for John Kerry?
Keene cited numbers which show that domestic social welfare spending has increased by $96 billion since 2001, compared to spending increases of $51 billion during Bill Clinton's first six years in office.
Some fiscal conservatives were livid when the Republican-led Congress passed a $400 billion Medicare bill last year with the support of the White House.
Gonzales says the bill upset many Republicans who felt the government was giving away money when "we didn't have the money to give away".
The administration has also angered some conservatives by pushing an immigration reform proposal that would give legal residency status to millions of undocumented workers, and by calling for Congress to make permanent several controversial measures of The USA Patriot Act.
Conservatives, such as former Republican congressman Bob Barr, who support the limited powers of the federal government, have denounced the law as a threat to fundamental civil liberties.
"If, however, the country is to retain some semblance of a Bill of Rights, including the guarantees against unreasonable searches and seizures, the vigilance of a Paul Revere and the resolve of a Winston Churchill, are needed now, more than ever," Barr wrote in a recent editorial.