Updated: Nov. 5, 12 a.m.

One hundred and forty-six years after President Abraham Lincoln ended slavery and some 40 years since the height of the civil rights movement, Sen. Barack Obama (D-Ill.) tonight became the first African-American to be elected president of the United States, defeating Sen. John McCain (R-Ariz.).

Obama’s win will put the Democrats in charge of the House, the Senate and the White House for the first time since 1994, marking a seismic shift from the solid GOP control on both ends of Capitol Hill that existed as recently as two years ago.

With Obama taking the presidency and running mate Sen. Joseph Biden (D-Del.) poised to be vice president, two Senators will take over leadership of the executive branch for the first time since Sens. John Kennedy (D-Mass.) and Lyndon Johnson (D-Texas) did so in 1960.

Appearing in Phoenix tonight, McCain conceded the election, pledging to do “all in my power” to help Obama lead the nation. “The failure is mine, not yours,” McCain told supporters. “I wish godspeed to the man who was my opponent and will be my president.”

McCain paid homage to Obama and the significance of the election of the first black American to the presidency, saying it had shown the progress the United States had made on race relations since an uproar accompanied the invitation of Booker T. Washington to the White House by President Theodore Roosevelt.

McCain also applauded the performance of his running mate, Alaska Gov. Sarah Palin, and nodded to her possibly promising future.

“We can all look forward with great interest to her future service to Alaska, the Republican Party and our country,” he said.

Obama showed strength early in the evening by taking Pennsylvania, a state where he was ahead but that McCain and Palin fought hard to take in the final weeks of the campaign. While McCain held some key states he needed to win, such as Georgia and West Virginia, the news that he had lost Ohio and its 20 electoral votes dealt a nearly fatal blow to his candidacy.

Once it became clear that he had dropped another major must-win state, Virginia, the networks called the race for Obama. Virginia has gone for the GOP presidential candidate since 1964, and no Republican has ever won the White House without winning Ohio.

McCain in the end faced too many headwinds to overtake Obama, who polled ahead of his Republican opponent for much of the campaign. Perhaps the strongest headwind was President Bush, among the most unpopular of modern presidents and, to McCain’s misfortune, a Republican. Obama carefully cultivated his image as an agent of change from the very beginning of his campaign two years ago, and events conspired to remind voters of why they were dissatisfied with the status quo.

In the critical weeks before Election Day the economy was in nearly constant turmoil, with the stock market repeatedly plunging hundreds of points in a day and banks refusing to lend. A rebound in the stock market in recent days was apparently not enough to convince voters to change their minds about Obama, who consistently polled as the candidate better-suited to right the tottering economy.

Though the situation in Iraq is better than it has been in years, voters remain strongly opposed to the war, and the worsening situation in Afghanistan perhaps exacerbated frustrations with Bush’s foreign policy. Obama has promised to withdraw U.S. troops from Iraq and focus on Afghanistan and on tracking down Osama bin Laden.

McCain may have added to his own woes. His selection of Palin as his running mate energized conservatives who had always been ambivalent about McCain. But her relative lack of experience partially denied McCain of one of his trump cards — the argument that Obama was far too green to be president — and her halting performance in early interviews raised questions among many voters about her fitness to be president.

While Obama stuck relentlessly to his themes of change and to proposals to revamp the nation’s health care system and allow a “middle-class tax cut,” McCain seemed to lurch around. Behind and increasingly desperate, he abandoned hopes to run a campaign devoid of attacks and began relatively late in the game to try to define his opponent as a risky choice. Bush, by contrast, won in part in 2004 by placing indelible, negative images of his opponent, Sen. John Kerry (D-Mass.) in the minds of voters early in the contest.

But it was the economy, which appears to be headed into what could be an extended recession, that probably sealed McCain’s fate and lifted Obama. Whoever is to blame for the upheaval in the economy, it was Bush who presided over its decline, and voters who decided to put a Democrat in charge instead.

Sen. Hillary Rodham Clinton, in a statement, said, “This was a long and hard fought campaign but the result was well worth the wait. Together, under the leadership of President Barack Obama, Vice President Joe Biden, and a Democratic Congress, we will chart a better course to build a new economy and rebuild our leadership in the world. And I look forward to doing all that I can to support President Obama and Vice President Biden in the difficult work that lies ahead.”

House Minority Leader John Boehner (R-Ohio) said, “I congratulate Senator Barack Obama on his election as the 44th President of the United States, an achievement that is an important milestone for our democracy.”