Former Rep. Stephanie Herseth Sandlin will not run for the Senate in South Dakota, a blow to national Democrats who had seen her as their strongest candidate to retain the seat.

In an announcement on her Facebook page Monday, Herseth Sandlin said she's declining a run for the Senate seat to be vacated by retiring Sen. Tim JohnsonTimothy (Tim) Peter JohnsonSenate GOP rejects Trump’s call to go big on gun legislation Court ruling could be game changer for Dems in Nevada Bank lobbyists counting down to Shelby’s exit MORE (D-S.D.) to spend more time with her family.

"After carefully contemplating [a campaign in 2014], my family and I have concluded that the future should continue to be focused on the plans we laid last year at this time," she said.

"We’re looking forward to more quality time with family and friends here in Sioux Falls, up at the farm and out on the river. And my career at Raven Industries is everything I had anticipated and more, and continues to be very highly rewarding."

The statement seems to indicate she's also unlikely to run for governor in 2014.

Democrats saw Herseth Sandlin as the candidate most likely to retain Johnson's seat for the party. Polls conducted by the Democratic Senatorial Campaign Committee (DSCC) showed her running competitively against former Gov. Mike Rounds (R), the only Republican in the race so far.

The National Republican Senatorial Committee (NRSC) characterized Herseth Sandlin's decision not to run as a recruiting failure on the part of Democrats, who last week also saw Georgia Rep. John BarrowJohn Jenkins BarrowOur democracy can’t afford to cut legal aid services from the budget Dem files Ethics complaint on Benghazi panel Barrow thanks staff in farewell speech MORE (D) decline a Senate run. Democrats are currently working to convince Kentucky Secretary of State Alison Lundergan Grimes (D) to run against Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellPolitical figures pay tribute to Charles Krauthammer Charles Krauthammer dies at the age of 68 Overnight Energy: EPA declines to write new rule for toxic spills | Senate blocks move to stop Obama water rule | EPA bought 'tactical' pants and polos MORE (R).

"The DSCC has failed to clear the track in several states for their candidate of choice. Now that they've been unable to land their chosen candidate in Kentucky, Georgia, and South Dakota – the Senate Democrats are left facing the awkward situation of having to support their 2nd, 3rd, or even 11th choice," said NRSC communications director Brad Dayspring.

DSCC spokesman Justin Barasky said an expected GOP primary in South Dakota will give Democrats an opportunity to win by weakening the GOP candidate. But Barasky didn't even name the only announced Democrat in the race, former House candidate Rick Weiland, in his statement.

"There will be a strong Democratic candidate that can seize on the divisive GOP primary and provide South Dakotans with a clear alternative to the dysfunction on the Republican side," Barasky said. 

He argued Rounds will be like former Wisconsin Gov. Tommy Thompson, a Republican defeated in a Senate race last year in that state.

"Mike Rounds is like the second coming of Tommy Thompson. He has a glass jaw and his big spending record and work in the private sector has never faced even one drop of scrutiny," Barasky said. "National Republicans simply cannot win the majority if they are only fighting it out in red states and to date they have failed to expand the map in any way." 

Weiland, a former President Clinton appointee and two-time House candidate, announced his intentions to run for the seat last week. 

He indicated, in announcing his run, that another potential contender — Brendan Johnson, son of the retiring senator — isn't likely to enter the race.

Johnson was considered a strong candidate, and some Democrats worried that a primary between him and Herseth Sandlin would cost them the seat.

Democrats were excited about Herseth Sandlin because many of her votes in Congress put her to the right of much of her party, and any Democratic contender will likely have to tack to the center to win in deep-red South Dakota.

Weiland, for his part, is a progressive Democrat, and has already received the support of a group of grassroots Democrats in his run. Though he's likely to draw other progressive groups to back his candidacy, it's unclear whether he'll be able to overcome the partisan leanings of the state, which voted for Republican presidential nominee Mitt Romney with nearly 60 percent in 2012.