President Bush exhorted Americans Tuesday to "do your duty" and vote in midterm elections that Republicans worry could tip the congressional balance of power to Democrats.

Even though Bush's name was not on the Election Day ballot, he sought steadfastly in recent weeks to influence its outcome.

On Tuesday morning, the president did just what he's been prodding voters to do on his campaign swing through 10 states: vote Republican. At sunrise, he strode into the Crawford Fire Station near his ranch just as Texas polls opened and did the last thing he could do for this party.

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Once he left the voting booth, Bush made a general appeal to all citizens to go out and vote.

"We live in a free society and our government is only as good as the willingness of our people to participate," said Bush, his wife, Laura, at his side and an "I voted" sticker on the lapel of his brown suede jacket.

"Therefore, no matter what your party affiliation or if you don't have a party affiliation, do your duty cast your ballot and let your voice be heard," Bush said.

The GOP says the president's five-day sprint through heavily Republican areas helped fire up the party's political troops. The hope is that the GOP's well-oiled, get-out-the-vote operation will be enough to fend off the Democrats' aggressive push to capture control of Congress.

Privately, however, Republicans acknowledge that their party has a slim chance of retaining the House after tight campaign races that, in many states, have turned into a referendum on the president himself, turmoil in Iraq and political scandals.

Bush, quick to denounce political prognosticators, put a positive spin his party's chances.

"I knew we were going to finish strong," Bush said at a rally in Arkansas where the audience was pumped up by a university band banging drums and cymbals. "I knew that we were going to come roarin' into Election Day because we've got the right position on taxes, we've got the right position on what it takes to protect you from attack."

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Sara Taylor, White House political director, said the president's presence helped at each stop on his final push to Election Day. For example, she said, Bush's trip to Sugar Land, Texas, on Oct. 30 helped the write-in candidacy of Shelley Sekula-Gibbs to replace former House Majority Leader Tom DeLay, who resigned amid investigations about his fundraising.

"He is energizing voters in contested races in areas where turnout will make the difference," Taylor said.

Still, the White House had to battle the perception that Bush was doing his party as much harm as good — and was unwanted in some districts. The White House did not hide its irritation when the Florida GOP gubernatorial candidate, Charlie Crist, skipped a chance to campaign at Bush's side in the Florida Panhandle. Crist said his support was firm there and it made more sense to campaign elsewhere in the state.

In recent history, the best any party has done when the popularity of the man sitting in the Oval Office has dipped below 50 percent was in 1978. That year, when President Carter's approval was 49 percent, his party lost 15 seats in the House, the same number that Democrats need to regain control of the House this year.

Out to beat the odds, Bush, his shirt sleeves rolled up, bounded onto the stage at each rally in Montana, Nevada, Missouri, Iowa, Colorado, Kansas, Nebraska, Florida, Arkansas and Texas.

Bush's schedule for the last lap took him to places like Elko, Nev., and other small to mid-size cities where he could create a buzz and draw wall-to-wall coverage from local media.

"The smaller the place, the more exciting it is," said Stephen Hess, a George Washington University public affairs professor who has worked in several Republican administrations.

"But what is it telling us that he's in Elko instead of Cleveland?" Hess asked. "He'd been better off if he could have been in places where he could be seen by 100,000 rather than 10,000."

At nearly every stop, several dozen protesters shouted and waved mostly anti-war signs at Bush's motorcade. One in Grand Island, Neb., said: "Stay the curse," a denunciation of Bush's "Stay the course" strategy in Iraq.

Did Bush sway voters in the south-central Nebraska town of 16,685?

"I don't think it's going to make that much of a difference," said Dwayne Niemoth, a disabled Vietnam veteran from Campbell, Neb. "I hope so, but I think it's pretty much decided."