The concession speech by Sen. George Allen, R-Va., today -- and the apparent victory of Democratic Senator-elect Jim Webb -- means that for the first time since 1994, Democrats control the Senate, the House and the agenda on Capitol Hill.
Webb, a former Republican who once served as Navy secretary for President Reagan, may hail from his party's more moderate wing. But his electoral success means many of his party's liberals will assume the leadership of domestic and foreign policy committees, bringing potential headaches to Bush.
"Will we stand up to the president when we think he is wrong?" asked Sen. Chuck Schumer, D-N.Y., the chairman of the Democratic Senatorial Campaign Committee, at a rally Thursday afternoon. "Yes. But our real job is to help the American family and make a better America."
That may be, but many Democratic senators assuming chairmanships also consider it their real job to hold the Bush administration accountable and to reverse policy decisions made when the GOP controlled the House and Senate.
"Some of the people who are taking over Senate committees are no friends of George Bush," said ABC News' political commentator Cokie Roberts. "They've made that very clear on several occasions."
Come January, the Judiciary Committee will be chaired by Sen. Patrick Leahy of Vermont, who has been one of the toughest critics of Bush's choices for judges and of his anti-terrorism measures.
Michigan's Carl Levin, who voted against the war in Iraq, will head the Armed Services Committee and conduct oversight hearings on the war.
West Virginia's Jay Rockefeller, a fierce critic of the administration's use of intelligence in the buildup to the war in Iraq, will helm the Select Committee on Intelligence.
Many domestic issues will be tackled by liberal lion Sen. Ted Kennedy of Massachusetts, who will head the Health, Education, Labor and Pensions Committee, which will play a leading role in the president's hope to renew the No Child Left Behind Act, Medicare and other contentious legislation.
Sen. Joe Biden, D-Del., takes over the Committee on Foreign Relations, and said the nomination of the president's ambassador to the United Nations, John Bolton, is dead on arrival.
"Republicans are having a bad day. It is no fun to lose the majority," Roberts said.
Added to that mix are seven Democratic senators harboring serious presidential ambitions for 2008, which will have them clamoring for the support of their party's liberal base, creating a real recipe of problems for Bush.
In the short term, Republican staffers who have enjoyed 12 years of dominance on Capitol Hill are now headed for job hunts.
"People are calling law firms and calling back home, and trying to find jobs anywhere they can," said Republican Senate staffer Jenny Manley.
Z. Byron Wolf and Jennifer Duck contributed to this report.