WASHINGTON — President Bush wasn't on the ballot, but he may have been the biggest loser in Tuesday's elections.

After crisscrossing the country on behalf of Republicans, Bush suffered a rebuke from voters that left him politically weaker than he's ever been. Democrats took control of the House of Representatives for the first time since 1994. Bush will return to work today as a lame-duck president, facing challenges that could make his final two years in office far more difficult than his first six.

Bush, who watched the returns at the White House with friends and political adviser Karl Rove, had no immediate reaction to the outcome. He'll hold a news conference Wednesday at 11 a.m. (MST) that's likely to bear little resemblance to his buoyant performance after the last national elections.

Two years ago, Bush claimed to have gained political capital from elections that returned him to office and increased Republican majorities in the House of Representatives and the Senate. The question now is whether he has enough left in his account to function effectively.

Political analysts say it's too early to count him out.

"The president is not going to be a hapless giant. The powers of the presidency are tremendous, and they remain tremendous," said Stephen Hess, a presidential scholar at the Brookings Institution, a center-left think tank.

Still, there's no question that Bush suffered a setback that will diminish his standing at home and abroad, at least in the short term. As he cast his ballot in Texas, the president urged Americans to join him at the polls.

"Let your voice be heard," he said. They did, but he probably didn't like what they had to say.

The Democratic takeover of the House eliminated Bush's best ally in Washington. Instead of a compliant, Republican-controlled chamber, he'll face a combative legislative body led by Democrats nursing six years of grievances against him.

The Senate, seldom as loyal to Bush as the House was, will be even less reliable than it has been. Although the final party lineup remained in doubt late Tuesday, the only unresolved question was how many seats Republicans would lose. Even if they retain a majority, it will be razor-thin — and Republican senators have been put on notice by the voters.

Democrats won't have enough votes in Congress to impose their plans with legislation, especially over Bush's veto, but they'll have enough to bottle up the president's initiatives and block controversial appointees to the Supreme Court or key administration jobs. Control of the House also would give them the power to launch investigations into every aspect of administration policy.