Washington (CNN) -- The Democratic dam has burst.
It started Wednesday afternoon when Mark Udall became the first Democrat in the Senate to call for embattled Veterans Affairs Secretary Eric Shinseki to resign.
Udall was soon joined by other members of the chamber, including John Walsh of Montana, an appointee, Kay Hagan of North Carolina, Al Franken of Minnesota and Jeanne Shaheen of New Hampshire.
What all have in common is that they're running this November for six more years in Washington, and other than Franken, they all face challenging contests in an already difficult midterm climate for Democrats.
Joining them were a handful of House Democrats, including Rep. Bruce Braley of Iowa. He's the party's hope for keeping the seat of retiring Sen. Tom Harkin in Democratic hands.
Weathering controversies from the IRS to the NSA to Obamacare, the last thing Democrats running for their political lives need is another scandal.
The political dam burst a couple of hours after a preliminary report from the VA Inspector General's office said that at least 1,700 military veterans waiting to see a doctor were never scheduled for an appointment and were never placed on a wait list at the Veterans Affairs medical center in Phoenix.
The VA controversy has mushroomed since CNN first reported last November on allegations of alarming shortcomings within the VA medical care system that potentially have had deadly consequences in dozens of cases.
The most disturbing and striking problems emerged in Arizona last month, with sources revealing to CNN details of a secret waiting list. According to the sources, at least 40 American veterans died in Phoenix while waiting for care at the VA there.
Richard Griffin, the acting inspector general, continues to investigate the matter, but his initial findings took the controversy to a new level -- an independent finding of serious problems around the treatment of veterans that appear to be national in scope.
Over the past couple of weeks Shinseki has come under pressure to resign from many Republican lawmakers and candidates, and that continued on Wednesday.
And Democrats outside Washington stumping for Senate seats in three red states -- Alison Lundergan Grimes in Kentucky, Michelle Nunn in Georgia, and Natalie Tennant in West Virginia -- recently joined the chorus.
But Democratic incumbents were waiting for the VA watchdog to speak, and now that he has, they no longer are holding out.
"The inspector general's preliminary report makes it clear that the systemic problems at the U.S. Department of Veterans Affairs are so entrenched that they require new leadership to be fixed," Udall said in his statement.
Thursday Democratic Sens. Jeff Merkley of Oregon, who possibly could possibly face a tough 2014 re-election, Mark Warner of Virginia and Tom Udall of New Mexico, who's re-elections are considered relatively safe, and Martin Heinrich of New Mexico and Tim Kaine of Virginia, who aren't up until 2018, also called for Shinseki to step down.
And so did Mary Landrieu of Louisiana, who is considered one of the most endangered Democrats bidding this November for another term in the Senate.
The announcements come as the Democrats try to hold on to their 55-45 majority in the Senate (53 Democrats and two independents who caucus with the party). The party's defending 21 of the 36 seats up in November, with half of those Democratic-held seats in red or purple states.
The smaller midterm electorate traditionally tends to favor the GOP. Add to that a climate that favors the Republicans, due to the sluggish economic recovery, President Barack Obama's low approval ratings, continued strong opposition by conservatives to the federal health care law and the so-called "six-year-itch," which traditionally plagues the party that controls the White House during a president's second term.
"This is a no-brainer for congressional Democrats: It's likely a matter of when, not if, for Shinseki given the clear failure in oversight, and it's important to get in front of that. This allows Democrats to show independence on a substantive issue," said a Democratic strategist and former official in the Obama White House, who asked to remain anonymous to speak more freely.
Democratic strategist and CNN contributor Paul Begala, a longtime senior political adviser to Bill and Hillary Clinton, said the Democratic calls for the VA secretary to resign look like "a cry for strong, dramatic action. General Shinseki did not cause the problem -- senators know that. But in the wake of the IG report more and more folks are calling for Shinseki's ouster."
But Republican strategist Kevin Madden thinks the damage has already been done.
"It's a sign of just how bipartisan the frustration with the Obama administration's incompetence has become," said Madden, a CNN contributor who was a top adviser in Mitt Romney's 2008 and 2012 presidential campaigns.
"The VA scandal just affirms an already existing judgment that a majority of voters have made about President Obama's poor performance," Madden add. "He's not meeting even minimum standards of efficiency when it comes to managing his own administration and, as a result, his performance rating will take a hit and so will his party," Madden added.
And GOP consultant Brian Walsh said the moves by the Democratic lawmakers may have come too late.
"From Obamacare, to the war on coal, to now the VA, Democrats facing voters this year are working feverishly to separate themselves from the failed leadership of (Senate Majority Leader) Harry Reid and President Obama. The problem is that for the last two years, all of them voted in lockstep in support of their agenda and all of them will have to account for that in November," said Walsh, who served as National Republican Senatorial Committee communications director the past two election cycles.
The Veterans Affairs scandal's been a major issue on the campaign trail over the past couple of weeks. And on Wednesday, it also became front and center in the campaign ad wars.
Crossroads GPS, the non-profit sister organization to American Crossroads, a leading pro-GOP outside group which was co-founded and steered by Karl Rove, went up with a television commercial in Alaska that's critical of Sen. Mark Begich over his reaction to the growing controversy. Begich is considered one of the most vulnerable Democratic senators running for re-election this year
"A national disgrace. Veterans died waiting for care that never came. Senator Mark Begich sits on the Veterans Affairs Committee. His response? If there's a problem, they need to fix it. If there's a problem?" said the narrator in the spot, which was the first major ad to focus on the scandal.
The VA scandal is also in a new ad attacking another vulnerable Democratic, Sen. Mark Pryor of Arkansas. The spot by Rep. Tom Cotton, the GOP challenger in the race, hits Pryor for what it says is his inaction in dealing with the controversy.
"What did Mark Pryor do? Nothing," said the narrator in the online spot.
Neither Begich or Pryor have yet to call on Shinseki to step down.
While Republicans see the scandal as a political gift, Begala isn't sure just how much the issue will resonate come November.
"The economy is going to drive the mid-term elections more than the VA scandal," Begala added.
Shinseki on VA scandal: 'We are not waiting to set things straight'
CNN Senior Congressional Producer Ted Barrett contributed to this story