"I know you'll join me in sprinting to the finish line," Mr Bush told hundreds of cheering supporters in a giant entertainment complex here as he opened a push through at least nine states to aid vulnerable Republican candidates.
"We will win the Senate and we'll win the House and we're going to win these elections because we understand the values and priorities of the American people."
Democrats, who have enjoyed an advantage in recent opinion polls, "think this election is over. They don't understand that the people of Montana haven't voted yet," Mr Bush said.
Mr Bush fired back at the Democratic attacks on his handling of the Iraq war, which has weakened him and could cost his party control of the Senate, the House of Representatives or both on November 7.
"The Democrats have no plan for victory, they have no idea how to win," he said, to jeers from the crowd.
"Harsh criticism is not a plan for victory."
"You can't win the war unless you're willing to fight the war," said Mr Bush defending his decision to order the 2003 invasion, which has killed more than 2,800 US soldiers.
"We're in the middle of a war on terror and one of the most fundamental fights is in Iraq. And yet the Democrats have no plan for victory. The only way we could fail is if we leave before the job is done. And that's exactly what the Democrats want to do," he said.
'Just say no' approach
Mr Bush also recited his warnings that the opposition party would effectively raise US taxes by letting his giant tax cuts expire, and that it had a "just say no" approach to giving the US government broad powers to battle terrorism.
"Democrats are going to raise your taxes… When it comes to taxes, the Democrats are going to tax whoever they find," Mr Bush warned.
He noted Democratic opposition to legislation validating his controversial policy of warrantless wiretapping and green-lighting secret CIA prisons and interrogation tactics that critics have called torture.
President Bush is on a six-day sprint through at least nine states, hoping to brighten the fortunes of struggling Republican candidates.
Mr Bush telling the crowd "my call for our fellow citizens is to leave the hall, find our fellow Republicans and tell them we have a duty to vote, find discerning Democrats and remind them about the stakes, find discerning independents and tell them what's at stake in this election. Work hard between now and election day. Turn out the vote."
Not far from the giant entertainment complex, on the President's route, about 20 protesters waved signs saying "US Out of Iraq," while two, apparently dressed to look like inmates at the US run Guantanamo Bay facility in Cuba knelt in orange garb with black hoods over their heads.
The Democrats needs to win 15 seats to capture the 435-seat House of Representatives and six seats to take the 100-seat Senate.