WASHINGTON – Despite a fresh four-year term stretching before him, President Bush may have to break into a political sprint to achieve his lengthy domestic policy agenda – including major reforms to Social Security, the legal system, and the tax code.

Second-term presidents have a short window of political power, political analysts say, before Congress becomes mired in the cautious considerations of midterm election politics. And in the final years of a second term, foreign policy often takes center stage.

At an inaugural luncheon yesterday, Mr. Bush said he was looking forward to putting his “heart and soul” into his second term. Circumstances may leave him no choice.

The president is embarking on a full agenda with one of the lowest approval ratings of any president in recent history entering his second term. This potential obstacle is tempered by the fact that the slim majority of Americans who elected him are fiercely loyal and enthusiastic in their support. Likewise, Mr. Bush helped Republicans gain seats in Congress last November.

The administration is preparing to capitalize on both of these points by using intensive lobbying in Congress and traveling the country to build on the grassroots support for his ideas.

Most important may be how the White House sets its priorities, because many political analysts doubt he can do everything on his to-do list.

“I would estimate that given history’s precedents, Bush has six to eight months to really accomplish big things, and then the midterm election cycle sets in and circumstances in Washington become very political,” a political scientist at the University of Virginia, Larry Sabato, said.

The president has said the creation of private Social Security accounts is a top priority, but it is unclear when and if there will be sufficient support from members of his own party to enact such a plan. Supporters of the measure want him to act as soon as possible.

“This is something that clearly has to be done in 2005,” the director of health and welfare studies at the Cato Institute, Michael Tanner, said. “Because 2006 is an election year, and … in an election year, they are barely able to do Mom and apple pie. After that, the president is a lame duck.”

At the moment, Republicans themselves are divided over how and whether to proceed.

The chairman of the House Ways and Means Committee, Bill Thomas, said this week that partisan divisions could quickly render the plan “a dead horse.”

Some supporters of private accounts argue that the only way to save the initiative is for the administration to present Congress with a specific plan, rather than wait for congressional Republicans to introduce their own.

“Left on its own, congressional debate will bog down in a sea of competing interest groups that are more interested in sound bites than in taking action,” wrote a Social Security specialist at the Heritage Foundation, David John.

But other backers fear that adopting details too soon will only give ammunition to opponents of the plan. Democrats themselves have been calling on Mr. Bush to put forward details in his next budget.

Many congressional Democrats, labor unions, and the Association for the Advancement of Retired Persons are already working hard to discredit the plan as both unnecessary and unwise before the president lays down specifics.

“The growing progressive force in American politics will draw a bright line in the sand when it comes to privatizing Social Security and cutting benefits,” said a spokesman for the umbrella group Campaign for America’s Future, Toby Chaudhuri.

Mr. Tanner said the Social Security debate is one in which the president’s personal involvement can make a crucial difference, both in steeling his own party and in selling the proposal to the public.

“They are looking to the White House to lead,” Mr. Tanner said of congressional Republicans. “The leadership would rather this went away, but there is a lot of pressure from backbenches and conservative activists to press forward.”

Mr. Bush is expected to discuss the issue in more detail in his State of the Union address, and legislative committees may take it up by late spring.

“This is a president who has never lost a vote he wanted to win. They are really going to pull out all the stops – mobilize the grassroots machinery, and deal-make and arm-twist in Congress. In the end, very few Republicans are going to go against the president,” Mr. Tanner predicted.

But the price of even moderate success on Social Security may be paid in other agenda items.

Restricting tort lawsuits is one administration priority that faces an uncertain fate in Congress. The president is unlikely to achieve all three of the tort proposals he has promoted in recent weeks: limitations on jury awards in medical malpractice cases, restrictions on class-action litigation, and the shifting of asbestos claims out of the courts and into a trust fund.

All have been attempted and failed in the Congress last term.

“The math still doesn’t work at all. No, there is no reason to expect there is going to be any significant change,” said a spokesman for the American Trial Lawyers Association, Carlton Carl.

However, some bits and pieces have a good chance of becoming law, speculated a conservative strategist and president of Americans for Tax Reform, Grover Norquist.

In what he called a “rifle-shot strategy,” Mr. Norquist said he is discussing with lawmakers the chances for narrowly tailored legislation, such as a cap on jury awards for damages in cases of medical malpractice strictly for obstetricians in rural communities, for example.

“You could do various pieces of medical malpractice reform, but I tend to think the one most likely to win is the rural exception,” he said, citing the departures of specialists from small communities.

Likewise, an incremental approach to tax reform is more likely to succeed than a root-and-branch overhaul of the tax code, he predicted.

“You do four years of incremental tax reform and you have gone a long way to anyone’s definition of tax reform,” he said.

The Congress could pass individual initiatives such as ending the estate tax, expanding Investment Retirement Accounts, limiting lawsuits against manufacturers of firearms, and even class-action suits, and expanding trade agreements, he said. “These are things we have the votes to do,” he said.

In contrast, the president’s desire to reform the immigration system and allow migrant workers to stay in the country legally may be one agenda item that will benefit from delay – as long as the economy continues to grow.

“We’ll wait until the economy and job market is so tight that those people who think that foreigners steal all those wonderful jobs in the hog-slaughtering industry don’t have that argument,” he said.

Of course, Mr. Bush’s influence in the final two years of his term will depend on the outcome of the 2006 elections. If Republicans once again return strengthened and emboldened, he will enjoy a second wind.

Moreover, the area that Mr. Bush telegraphed in yesterday’s speech would be the central preoccupation of his second term – foreign policy – is less affected by congressional mood.

“Presidents tend to focus on foreign policy in their second term,” Mr. Sabato said. “Once their influence in Congress is on the wane.”