Washington ? President Bush is ready to challenge Congress to approve a stack of politically divisive measures he has proposed before without success, from major changes in Social Security to a loosening of the nation’s immigration laws.

Bush will go before Congress and the nation with his annual State of the Union message tonight with the lowest approval rating of any second-term president since Richard Nixon. Yet he is in a feisty mood, insisting that his re-election has given him a mandate for change and political capital to spend in pursuing his agenda.

Even though Republicans control both houses of Congress, Bush’s proposals face major obstacles. Democrats are deeply suspicious of the president, feeling he has ignored them and refused to compromise.

The poisonous relationship between Republicans and Democrats also complicates Bush’s task.

“We have the most polarized Congress maybe since the 1930s,” said Terry Madonna, a professor and pollster at Franklin & Marshall College in Lancaster, Pa. “I don’t think there’s any way Democrats are going to roll over on these issues that they feel very strongly about. Bipartisanship is virtually obsolete in Congress.”

Bush will use the State of the Union address to update the nation on Iraq after Sunday’s elections, discussing the way forward, aides said.

The key ingredients of Bush’s domestic package — Social Security, an energy bill, limits on medical malpractice lawsuits, immigration — are repackaged from years past.

“These are oldies, golden oldies,” said Norman Ornstein, a political analyst at the conservative American Enterprise Institute. “Much of what is on the agenda in domestic policy are things that made it around the track in the first four years but didn’t get to the finish line.”

The president will “talk in certainly greater detail” tonight than he has in the past about his plan to restructure Social Security, White House spokesman Scott McClellan said.

“I think you can expect that a good portion of his State of the Union address will talk about the need to save and strengthen Social Security for our children and grandchildren,” McClellan said. “This is about fixing a problem that faces younger Americans and future generations. And we need to act on this opportunity that’s before us, because it only gets worse over time.”

McClellan said Bush also would talk about the U.S. economy.