Longtime Senator Arlen Specter Loses Bid for Sixth Term to Congressman Joe Sestak

In a symbol of the growing anti-Washington sentiment across the country, Rep. Joe Sestak defeated five-term senator Arlen Specter in the Pennsylvania Democratic Senate primary and in Kentucky, Tea Party-backed candidate Rand Paul captured GOP Senate nomination, defeating GOP establishment candidate and Secretary of State Trey Grayson.

Specter, a longtime Republican, switched parties in April of 2009 to avoid a potential defeat against his likely GOP opponent Pat Toomey. But Sestak, a virtual unknown compared to his incumbent opponent, successfully exploited the anti-Washington mood and campaigned around Specter's decision to switch from the Republican to the Democratic Party last year.

VIDEO: Voters Send D.C. a MessagePlay
Voters Send D.C. a Message

Specter took the stage shortly after it became clear he was going to lose the race and thanked his family, staff and supporters, including President Obama and Vice President Biden.

"It's been a great privilege to serve the people of Pennsylvania, and it's been a great privilege to be in the U.S. Senate," a visibly emotional Specter said. "I will be working very hard for the people of the Commonwealth in the coming months."

Specter also tweeted a congratulatory message to his rival.

"Congratulations, Congressman Sestak. You have my support for the general election," Specter wrote.

VIDEO: Rand Paul defeated the established GOP candidate to capture Senate nomination.Play
Tea Party Scores Big Win in Kentucky

A jubilant Sestak praised Specter and thanked him for his service, but had some pointing words about incumbents.

"Too many career politicians are a bit too concerned about keeping their jobs rather than serving the public, helping the people," Sestak said in a speech reflective of his campaign against Specter.

A spokesman for the Pennsylvania Department of State told ABC News earlier today that turnout was "relatively light" versus comparable past elections, especially in Philadelphia, where Specter's main supporter base was concentrated.

Specter served as one of two senators from Pennsylvania for nearly 30 years. He was first elected to the seat in 1980, and through the years survived many tight races and challenges, including against Toomey in 2004.

Midterm Election PrimariesPlay
Midterm Election Primaries

But what jolted Sestak's visibility in this primary was a television ad showing Specter with President George W. Bush and Sarah Palin. Sestak also played upon Specter's party switch, painting him as a politician who made the move for his own political gain and to save his job rather than for his constituents.

Specter was backed by the White House -- although neither Obama nor Biden campaigned with him in recent days -- as well as other heavy hitters in the state like Gov. Ed Rendell. Those supporters who now have to switch their allegiance to Sestak cautiously congratulated both candidates while quickly aligning themselves behind the new Democratic candidate for the seat.

"Congressman Sestak and Senator Specter both campaigned tirelessly across the Keystone State in support of President Obama's efforts to help middle-class Americans. I congratulate them both on a hard-fought campaign," Democratic National Committee chairman Tim Kaine said in a statement.

Sen. Robert Menendez, D-New Jersey, chairman of the Democratic Senatorial Campaign Committee said both men deserved credit for "waging thoughtful, spirited campaigns."

On the Republican front, former Congressman Toomey secured the GOP nomination, as expected, and will face Sestak in the midterm election.

Democrats Win Pennsylvania Special Election

In the western Pennsylvania special House election to replace the late Rep. John Murtha, Republican Tim Burns called and conceded the race to Democrat and former Murtha aide Mark Critz.

The race was painted by Republicans as a referendum on the "Obama-Pelosi agenda" and Republicans are now likely to face questions about whether or not, even in this environment, just criticizing the "Obama-Pelosi" agenda as Burns had done through this entire campaign is sufficient. This district was precisely the kind of district that Republicans needed to win in order to become the majority party this fall.

Republicans will argue that the turnout advantages for Democrats in a special election on primary day with a competitive Democratic primary at the top of the ticket were too great to overcome, but that they will win this seat in November.

National Republican Congressional Committee Chairman Pete Sessions, R-Texas, called the results of the special election "undoubtedly disappointing" but vowed to take a lesson from it for the November midterm elections.

"This hard-fought race gave us an early preview of what Democrats will attempt to do in the fall in order to survive," Sessions said in a statement. "They will steer clear of publicly campaigning with President Obama and Speaker Pelosi, distance themselves from the Democratic agenda, and attempt to co-opt Republican positions on the issues. The bottom line is that the makeup of the House remains the same and our goal of winning back the majority in November has not changed."

Kaine billed the victory as a "significant blow" to the Republican party.

"Tonight's result demonstrates clearly that Democrats can compete and win in conservative districts," he said in a statement. "The Republican Party's failure to take a seat that they themselves said was tailor made for them to win is a significant blow and shows that while conventional wisdom holds that this will be a tough year for Democrats, the final chapter of this year's elections is far from written."

Arkansas Sen. Blanche Lincoln Faces Runoff

In Arkansas, incumbent Sen. Blanche Lincoln, D-Arkansas, facing the toughest political battle of her career, failed to win the majority of votes in the Democratic primary. She will now face a runoff election with Lt. Gov. Bill Halter on June 8.

Lincoln was the target of much of the same anti-incumbent sentiment as Specter. But unlike the Pennsylvania senator, she did garner a majority of the votes, but not the 50 percent needed to avoid a runoff.

"Three more weeks, two more candidates, one choice for change," an enthusiastic Halter said in a speech tonight. "Today Arkansans had their say. If you send the same people to Washington, you'll get the same results."

The turnout in the Arkansas primary was projected to be roughly 31 percent. The turnout for the primaries is usually in the mid-twenties so the number is "above par," a spokeswoman for the Secretary of State's office in Arkansas told ABC News. She said they received 125,000 absentee and/or early votes and that usually makes up about 25 percent of the electorate.

Despite her moderate record, being a Democrat in Republican-trending Arkansas in this political environment made Lincoln one of the most vulnerable incumbent Democrats up for re-election this year.

Labor unions poured more than $5 million into Halter's candidacy as he slammed Lincoln for voting for the bailout for banks and opposing the Employee Free Choice Act or card check, which is a high priority for the labor movement.

Lincoln voted for the health care bill and touted that vote heavily in her television commercials. Halter, however, also supported Obama's health care plan and unlike Lincoln, he also backed the option of a government-run health insurance plan that would compete with private insurers, a more liberal option that was stripped from the health care bill in the Senate to garner the votes of moderate Democrats.

Voters interviewed by ABC News overwhelmingly demonstrated anti-Washington sentiment prevalent across the rest of the country.

"I think people generally are unhappy with how Congress as a whole has behaved and I think what we'll see nationally is a lot of incumbents will be voted out of office, regardless of what party they're in," said voter Roberta Monson.

Another voter Becky Dugan said she supported Lincoln but understood the frustration among her peers.

"I like the direction the country is going. I like that we're in the direction of taking care of people," she said, but many people are "just frustrated. And I think when the economy has a downturn and we get worried, that frustration is an expression of that worry. More worry. Fear."

Click back for results and projections as the polls close: Arkansas | Kentucky | Oregon | Pennsylvania

Tea Party Supporter Rand Paul Wins Kentucky Republican Primary

In Kentucky, longtime Congressman Ron Paul's son, ophthalmologist Rand Paul, was declared the winner of the Republican Senate primary shortly after polls closed. With more than half of the precincts reporting, Paul had a wide lead over Grayson.

Fueled by grassroots momentum and his father's donor base, Paul was predicted to be a favorite since the beginning.

Whether he eventually wins the Senate seat will be an indication of the strength of the Tea Party movement.

2010 Elections Map: Follow the Senate, House and Governors' Races

"I have a message, a message from the Tea Party," Paul said in a speech to his supporters. "We've come to take our government back."

"Washington is horribly broken," he added. "I think we stand on a precipice. We are encountering a day of reckoning and this movement -- this Tea Part movement, is a message to Washington that we're unhappy and we want things done differently."

Grayson was backed by some of the most powerful Republicans in Washington, including former vice president Dick Cheney and Senate Minority Leader Mitch McConnell, R-Ky., who especially handpicked Grayson. But Paul, a rookie politician, has been a supporter of the Tea Party since its inception and also secured the support of another Tea Party favorite, former Alaska Governor Sarah Palin.

McConnell congratulated Rand and promised to back him in the race against Democrats.

"Dr. Paul ran an outstanding campaign which clearly struck a chord with Kentucky voters and I congratulate him on his impressive victory," McConnell said in a statement. "Now Kentucky Republicans will unite in standing against the overreaching policies of the Obama administration. We are spiraling further into unsustainable debt and Kentucky needs Rand Paul in the U.S. Senate because he will work every day to stop this crippling agenda."

Outside polling stations today, Paul's supporters cheered and waved his signs.

"I did not vote for any incumbent. Any incumbent I want out. We need change, period," resident Rickie Eadens told ABC News.

Another voter, Brad Leix, said he voted for Paul because he is not a Washington insider.

"I'm just tired of the government insiders. You've got certain people who've been in office for so long. We need some outside views that aren't afraid to rock the boat a little bit. So, I think that people like him will be good for the country," Leix said.

A spokesman for the Kentucky Secretary of State's office told ABC News that turnout was low and absentee voting was down 16 percent from the previous primary.

Kentucky's liberal Attorney General Paul Conway, won the Democratic nomination. Conway was running against the more conservative Lt. Gov. Dan Mongiardo, who opposed President Obama's health care plan.

ABC News' Andrew Fies contributed to this report.