In the biggest election of the night, President Obama defeated Republican challenger Mitt Romney to serve a second term in the presidency. Scott Wilson and Philip Rucker discuss the strategy that led the president to victory:

In early spring, President Obama’s veteran campaign staff in Chicago confronted the question that would ultimately determine the presidency: how to run against Mitt Romney?

The choice discussed on frequent calls between the White House and One Prudential Plaza was whether to campaign against Romney as a flip-flopper — a former centrist governor of Massachusetts who turned conservative to win his party’s nomination — or use his career as the head of Bain Capital to cast him as a protector of the privileged at the expense of the middle class.

“The most striking data we saw early on was on the ‘understands problems of people like me’ question,” said a senior White House official involved in the discussions. “Into the summer, Romney was in the teens in this category.”

The choice was made. The onetime campaign of hope and change soon began a sustained advertising assault that cast Romney as a heartless executive, a man who willingly fires people and is disconnected from how average Americans live their lives — an approach reinforced by Romney’s mistakes along the way.

While the Obama campaign bet it could set the campaign’s course in the summer of 2012, Romney’s senior staffers in Boston put their money on winning a decisive autumn, when it believed voters would tune in to the race in earnest and their jobs-first message would convince the nation it was time for a change.

In one of the most closely watched Senate races in the country, Democrat Elizabeth Warren defeated Republican incumbent Scott Brown to take a Massachusetts seat held for decades by liberal icon Edward M. Kennedy. Stephanie McCrumment writes:

Democrat Elizabeth Warren, a Harvard law professor and bankruptcy expert who has spent her career documenting the decline of middle-class America, won the hotly contested Senate race in Massachusetts on Tuesday night, defeating Republican incumbent Scott Brown and reclaiming the seat held for decades by liberal icon Edward M. Kennedy.

Warren, who rose to national prominence as chair of the congressional panel overseeing the 2008 Wall Street bailout, is the first woman to be elected U.S. senator from Massachusetts.

“This victory belongs to you,” she told a raucous and jam-packed crowd at her headquarters in Boston. “You did this for every family that has been squeezed and hammered. We are going to fight for a level playing field and we are going to put people back to work. To all the small-business owners who are tired of a system rigged against them, we’re going to hold the big guys accountable.”

“I will always carry your stories in my heart,” Warren said. “I will be your champion.”

Just moments earlier, Brown, a pickup truck-driving Republican who stunned the political establishment by winning a special election after Kennedy’s death, conceded the race to Warren.

“You know what the most difficult part is?” Brown, who won over voters in this bluest of blue states with his considerable regular-guy charm, asked supporters Tuesday night. “I now have to be breaking the news to my truck that I’ll be taking it home.”

Progressives cast the victory as a “historic moment” for working families, saying Warren would “shake up the corridors of power from Washington to Wall Street.” Sen. John F. Kerry (D-Mass.) said it was not only “a big night for Massachusetts but an enormous night for our country.”

Rep. Tammy Baldwin (D) also made waves when she defeated former governor Tommy Thompson (R) to take Wisconsin’s open Senate seat. Rachel Weiner writes:

Baldwin will take over for retiring Sen. Herb Kohl (D); she will be Wisconsin’s first female senator and the country’s first openly gay senator. But, she told supporters at a party in Madison, “I didn’t run to make history.  I ran to make a difference.” 

She reached out to her opponent and his supporters, promising to represent all Wisconsinites. “Tommy and I didn’t agree on much in this campaign but there can be no doubt that he shares my love for Wisconsin,” she said. “And even at the end of a long and sometimes bitter campaign, I’m still grateful for his service to our state.” 

Baldwin’s win was part of several key ones for Senate Democrats that will help them retain their majority. More on her race from The Fix

Despite losing a few seats in the Senate, Republicans won enough votes to retain control of the House of Representatives. Paul Kane writes:

Republicans won enough crucial races Tuesday to retain control of the House of Representatives, beating back a strong Democratic challenge and allowing the GOP to keep pushing an agenda of fiscal austerity.

The GOP was on track to hold on to a strong majority in the chamber, ensuring that House Speaker John A. Boehner (Ohio) remains the dominant Republican legislator in negotiations over government spending in the months ahead. With results tallied in much of the country, Republicans appeared close to maintaining at least a 20-seat margin.

The continued GOP dominance in the House probably will lead to renewed clashes with Senate Democrats, with whom Boehner’s conservative caucus feuded for the past two years in budget battles that brought the federal government to the brink of defaulting on its debt.

Those partisan showdowns made the 112th Congress the least-popular in history. Although that seemed to bode ill for incumbents — several in both parties fell to primary challengers in the spring and summer — voters Tuesday followed an old axiom: They loathe Congress but support their local congressman.

Many incumbents survived because of a redistricting process that left a record-low number of competitive seats, cloistering Republicans and Democrats together into geographically odd — but politically homogenous — districts. In Florida, where population growth boosted the delegation to 27 seats, only six races were considered competitive entering Election Day.

Rep. Michele Bachmann (R-Minn.), founder of the Tea Party Caucus and an unsuccessful candidate for the GOP presidential nomination, hung on to her House seat by narrowly defeating challenger Jim Graves. Debbi Wilgoren writes:

Bachmann, whose controversial statements leading up to the election included accusing President Obama of “apology and appeasement across the globe,” was declared the winner by the Associated Press with 98 percent of precincts reporting. She led Graves, a prominent businessman, by just over 3,000 votes out of nearly 350,000 votes cast.

Bachmann released a statement:

“It has truly been an honor and a privilege to represent the people of Minnesota’s Sixth District in Congress, and I am humbled that they have placed their trust in me for another term. I am extremely grateful to my dedicated volunteers for spending countless hours knocking on doors and making phone calls,” said Bachmann. “I pledge to continue to work everyday to create jobs and do everything I can to make life more affordable for Minnesota’s families. Our children and grandchildren deserve a future filled with opportunity in a country that is safe and secure, and that’s what I’m fighting for in Washington.”

For more election results and analysis, view the Post’s elections results map.