Nowhere was that clearer than in Pennsylvania, with a furious effort stretching from the White House to local party leaders who sought to prop up Democrat Katie McGinty, who was struggling in the polls just a few weeks ago.
But with millions poured over the airwaves by the Senate Democrats' campaign arm, and Joe Biden stumping alongside McGinty in recent days, the Democratic establishment helped McGinty secure a victory over a man party leaders have long viewed as a persistent agitator: former Rep. Joe Sestak. McGinty, a former chief of staff to Gov. Tom Wolf, will now face off against first-term GOP Sen. Pat Toomey -- in one of the country's most high profile Senate races.
"Katie McGinty has the best chance of beating Toomey -- we always felt that way," said Sen. Chuck Schumer, the likely next Democratic leader who helped recruit McGinty to run against Sestak. "We want to beat him."
McGinty's victory came just hours after party leaders scored another victory -- this time in Maryland, with the victory of Rep. Chris Van Hollen over the progressive Rep. Donna Edwards
, who had the backing of liberal women's groups in the contentious race. While the Democratic Senatorial Campaign Committee was neutral in Maryland, Van Hollen had the backing of many top Democrats, including Senate Minority Leader Harry Reid, in a race that fractured along gender and racial lines.
Van Hollen is heavily favored to succeed liberal Sen. Barbara Mikulski in the Democratic state, where he'll face off against Republican Kathy Szeliga this fall.
Also on Tuesday, Rep. Chaka Fattah, a veteran Democratic congressman indicted on corruption charges last year, lost his primary to state Rep. Dwight Evans in the battle to represent the Philadelphia-area district.
But the Pennsylvania Senate race has the biggest implication of Tuesday night's down-ticket races, with Toomey's seat at the heart of the national Democratic effort to retake the Senate majority. Democrats in Washington calculated that McGinty was a superior candidate over Sestak, who has a history fraught with tension with his congressional delegation and party leadership.
"Not at all," said Rep. Bob Brady, a 10-term congressman, when asked if Sestak works well with others. "He dances to the beat of his own drum. We need people to be cooperative and work together."
The fact that Democrats have so aggressively targeted Sestak has been rather remarkable given that the former two-term congressman lost by just two points when he faced off against Toomey in 2010. But it's how Sestak waged that campaign that has kept tensions raw with party bosses.
Republicans are eager to capitalize.
"Needless to say, a divisive primary hurts the Democratic nominee," Sen. Roger Wicker, chairman of the National Republican Senatorial Committee, said of the race. "We're not shedding any tears about the fact that it's been a rough-and-tumble primary."
"Ms. McGinty is not the best when it comes to discussing issues," Wicker told CNN. "She leaves a lot to be desired when it comes to articulating Pennsylvania values."
Shortly after President Barack Obama was sworn into office in 2009, Biden and Democratic leaders wooed the late-Sen. Arlen Specter, a long-time moderate Republican, to switch parties, effectively giving the White House a resounding supermajority in the chamber. The party establishment agreed to back Specter in the 2010 Senate race, but Sestak wouldn't listen.
Despite an aggressive lobbying campaign urging Sestak to bow out, he surprised his colleagues by announcing a run -- a move that energized the left-flank of his party that distrusted the long-time Republican Specter. Further embarrassing the White House, Sestak said that the Obama administration offered him a job to stay out of the race -- something that became a major distraction in the early days of the new White House.
With the backing of the base, Sestak won the primary but barely lost to Toomey in a tea-party-dominated election cycle. As the 2016 election began to move closer, Sestak made clear that he wanted to run again -- prompting concerns from party elders. The Democratic Senatorial Campaign Committee and Reid tried to make amends, meeting with Sestak and urging him to name veteran party operatives to professionalize his staff and begin raising loads of cash.
Yet the two sides never saw eye-to-eye, and Sestak took the unusual but headline-grabbing move of walking 422 miles across the state.
The DSCC, Schumer and Reid began to court other candidates but ran into resistance, including when Josh Shapiro, chairman of the Montgomery County Board of Commissioners, passed on a Senate bid. They then turned to McGinty, who threw her hat into the ring last summer.
The party establishment has pulled out all the stops, including with Biden stumping with McGinty this week and the DSCC spending at least $1.1 million on TV so far.
Sestak has been unsparing in his criticism of the party elite.
"More than anything, I want the trust of the people I will serve; that I am for them," Sestak said in a recent statement. "It is why I have not asked for any politician's endorsement. Perhaps too many of our politicians in both parties have acquiesced ... and maybe that is why the general public -- from the old tea party to today's progressive Democrats -- have felt attracted to those who seem to break the system."
Sen. Bob Casey, the senior Democratic senator, threw his support behind McGinty as well but said he would work to repair the wounds after Tuesday night.
"No matter what the results are tonight, we will unify," Casey said. Asked how the party would do that, Casey said: "Hard work -- and time."