Updated 12:20 p.m. -- Democrat Sen. Jay Rockefeller will not seek a sixth term in 2014, giving Republicans a chance to pick up a Senate seat next cycle. 

The news comes after Republican Rep. Shelley Moore Capito said that she would seek Rockefeller's seat. 

Rockefeller, 75, held a press conference to announce his decision this morning. 

A descendent of famed oil baron John D. Rockefeller, the West Virginia lawmaker's family legacy is rich with politics; New York Gov. Nelson Rockefeller and Arkansas Gov. Winthrop Rockefeller were his uncles. 

Rockefeller moved to West Virginia in the 1960s. He held the governorship for eight years before winning election to the Senate in 1984.

He easily won his last race in 2008, defeating his GOP opponent by a 64%-36% margin. But given West Virginia's more conservative tilt -- at least in presidential elections -- winning re-election in 2014 would have been far from guaranteed. 

The National Republican Senatorial Committee said in a statement that Rockefeller's departure represents "a strong pickup opportunity" in 2014.

"Voters next year will have a clear choice between a Democrat who will be a loyal vote for President Obama and Harry Reid as they try to kill West Virginia’s coal industry and bankrupt our country with reckless government spending, versus a Republican who will serve as an effective check-and-balance on their liberal agenda and work to get our country’s economy back on track," NRSC executive director Rob Collins wrote. 

NBC's Carrie Dann contributed to this report. 

President Obama headed toward wins in both primaries Tuesday in Arkansas and Kentucky, but suffered losses of about 40 percent of the vote in each contest against token opposition.

Over four in 10 Democratic voters in Kentucky's primary on Tuesday chose the "uncommitted" option versus President Barack Obama, who won the state's primary. 

And perennial candidate John Wolfe, Jr. took just about 40 percent of the primary vote versus Obama in Arkansas, according to early returns tabulated by the Associated Press. (Wolfe won't be awarded any delegates, either.) 

The president's performance in both contests carries no substantive importance; Obama has already scored the necessary delegates in previous caucuses and primaries to be re-nominated by Democrats, and he wasn't expected to win either Arkansas or Kentucky in the general election versus Mitt Romney.

But the primaries carry a degree of symbolic weight, if only to fuel Republicans' gawking about how an incumbent president could fare so poorly in primaries despite facing no meaningful opponent. 

Romney wins Kentucky, Arkansas primaries

Obama lost 65 of 120 counties in Kentucky to the uncommitted option, though most of those counties were lost by a slim margin, in some of the least populous counties in the state.

But Republicans have been especially eager to point toward the fact that Kentucky's primary is closed only to Democrats, meaning that some portion of the state's Democrats had to turn out at the polls (likely to participate in other contests on the ballot), and decide to explicitly oppose a president of the same party. 

Lessons learned from inmate's challenge to Obama in W.Va.

That was the same case in the West Virginia primary earlier this month, when convicted felon Keith Judd won about 41 percent in a similarly uncompetitive primary. 

But all three states — West Virginia, Kentucky and Arkansas — are home to either Appalachian or white, rural poor voters with whom Obama has traditionally struggled and historically underperformed in 2008 versus other Democratic presidential candidates. Some political observers have suggested that Obama's race has unduly weighed on his prospects in those ares. Moreover, turnout in each contest was especially low, opening the door for swings in the vote.

The general election, though, won't generally be fought in states where these voters make up a large portion of the electorate, more likely making Tuesday's primary results a footnote to the 2012 campaign than a dominating theme.

Vice President Joe Biden stayed mostly on message during a two-day swing in eastern Ohio this week, but one comment made to a local TV news station may have earned him some rolls of the eye at Obama campaign headquarters in Chicago.

In an interview yesterday with WTOV-TV, NBC's Steubenville-Wheeling affiliate, Biden said that he doesn't "blame people" for voting against Barack Obama in West Virginia's Democratic primary earlier this month, when an incarcerated felon won about four in 10 votes against the sitting president.

"Look, I come from a household where whenever there's a recession, somebody around my grandpop or my dad's table lost their job - a brother, a sister, a friend, a neighbor," he said.  When you're outta work, man, it's a depression. And a lot of people are still hurt because of this God-awful recession we inherited that cost 8.4 million jobs before we could really get going. And so I don't blame people. They're frustrated. They're angry."

Biden quickly pivoted to make the case that the administration's economic values would prevail nationwide over Mitt Romney's in the general election.

"At the end of the day they're going to decide is the way back to their employment, is the way back to being able to have a job and raise a family, is it under the value set and the ideas of Romney? Or is it under ours? And we feel confident we'll do just fine. "

Keith Judd, also known as Prisoner 11593-051, is serving a sentence at the Beaumont Federal Correctional Institution in Texas for making threats at the University of New Mexico. He makes occasional cameos on state ballots and won about 40 percent of the vote in West Virginia's May 8 primary, embarrassing national Democrats and highlighting Obama's challenges in coal country.

This image provided by Keith R. Judd shows the federal prisoner Keith Russell Judd, 49, at the Beaumont Federal Correctional Institution in Beaumont, Texas in this March 15, 2008 file photo.

The name of the federal prisoner -- Keith Judd -- who won 41 percent of the vote versus President Barack Obama in Tuesday's West Virginia Democratic primary isn't as important as the fact that the incumbent commander in chief won only 59 percent of the vote.

Republicans have giddily seized on Obama's relatively poor showing in the primary as an indicator of weakness. Though, it's notable that Obama has never performed particularly well in West Virginia, and he's not expected to carry the state versus Mitt Romney in the general election.

Even in a Democratic wave year, Republican John McCain beat Obama in West Virginia by a 13-point margin. And in the Democratic primary that same year, even though the race for the nomination appeared virtually over, Hillary Clinton crushed Obama, 67 percent to 26 percent.

Related: First Thoughts: The margins told the story

While West Virginia traditionally elects Democrats to statewide office, it is culturally conservative. West Virginia’s relatively poor residents rely heavily on pork projects from the government, as well as programs like Medicare and Medicaid. (A recent USA Today analysis found that West Virginia gets 28 percent of its income from government programs, more than any other state. Also, its population is second oldest in the nation, behind Florida.)

Even though many of those factors would seem to point toward support for Obama, the president has just simply never been popular there. One of the few areas in 2008 where McCain improved over past elections was Appalachia, an area that overlaps heavily with West Virginia's population.

But is there a cautionary tale for Democrats in the somewhat amusing scare led by Judd, who's serving a 17-and-a-half-year federal prison sentence in Texas after being convicted of making threats at the University of New Mexico?

The peculiar Obama effect in West Virginia has been apparent in the actions of the state's junior senator, Democrat Joe Manchin. A former governor of the state, Manchin tacked well to the right in his bid for the seat of the late Democratic Sen. Robert Byrd in 2010.

So blunt were Manchin's efforts to distance himself from Obama that he released a TV ad that cycle showing him shooting a copy of the president's signature health care law.

Even though he won the 2010 election, he's been a thorn in Obama's side since joining the Senate, accusing him of failing to lead the charge on cutting spending last year.  In a statement last month, Manchin said, “I have some real differences with both Gov. Romney and the president, as I have said many times."

But because Manchin won his seat in a special election, he must run for a full term again this November.

Related: Against Obama, even a jailbird gets some votes

"Stimulus deficit spending? Manchin is your man. The Obama agenda? Joe is on board more than 85 percent of the time," John Raese, Manchin's Republican opponent in 2010 who's challenging the senator again this fall, wrote Wednesday in the Charleston Gazette.

Democratic West Virginia Gov. Earl Ray Tomblin has also been coy about whether he'll even vote for Obama this fall. ("His policies will put more burdens on West Virginia families who are simply trying to make ends meet," he said earlier this month.)

But Republicans have also targeted longtime Democratic Rep. Nick Rahall, who's been more vocal about his support for Obama.

"Obama losing six counties in the 3rd District to a Texas prison inmate is the canary in the coal mine that Rahall’s 36-year career in Congress is coming to an end," said Nat Sillin, a spokesman for the National Republican Congressional Committee, in a statement.

There are plenty of other examples of instances in which Democratic candidates have sought to manage the extent to which they're tied to Obama. Republicans in some states have also had to wrestle with being tied to Romney.

According to a Democratic strategist familiar with the party's Senate campaign efforts, this is isn't atypical behavior. "I don't know that it changes all that much from one state to another. When our candidates agree, say so. When they disagree, say so."

Updated 8:50 p.m. — Mitt Romney added to his delegate count on Tuesday by sweeping the first set of primaries since his main Republican rivals have both ended their campaigns.

The presumptive Republican nominee won the primaries in Indiana, West Virginia and North Carolina, according to Associated Press projections. Between those three states, a total of 107 delegates were at stake in Tuesday's primaries.

Follow full primary results here

Romney entered the contests having won 856 of the 1,144 delegates needed to formally secure the nomination. North Carolina awards 52 delegates, allocated proportionally by statewide vote, while Indiana awards three delegates to winner of its nine congressional districts. West Virginia's delegates are all elected directly on the ballot.

These contests were the first since former House Speaker Newt Gingrich dropped his bid for the Republican nomination, and the first since former Pennsylvania Sen. Rick Santorum's late-night endorsement of Romney on Monday.

Texas Rep. Ron Paul has continued with his campaign, which has involved an additional strategy of picking off delegates in states that delay formal allocation of delegates to candidates.