National Democratic groups are on pace to spend more than $900,000 on the May 7 special House election in South Carolina — a sign party activists worry embattled former Gov. Mark Sanford (R) remains a threat to defeat Elizabeth Colbert Busch.  

The spending barrage underscores the strength of the Republican brand in the inexpensive district, which GOP presidential nominee Mitt Romney carried by 18 percentage points in 2012. 

The flood of cash to aid Colbert Busch reflects how perceptions of the race have changed in the two weeks since Sanford was accused of repeatedly trespassing on his ex-wife’s property. 

Before the revelations, Democrats would have been delighted at the prospect of a nail-biting close in the deep-red district.

Now a Colbert Busch loss to a Republican candidate beset by personal woes and disavowed by national Republicans could be viewed as something of a disappointment for Democrats. 

“The conventional wisdom inside the Beltway is a little too taken by the trespassing stuff,” one national Democratic strategist following the race told The Hill. 

“Does that mean we’re not going to win? No. But this is a too-close-to-call, margin-of-error race.”

The Democratic establishment has been all in for Colbert Busch in the closing weeks of the campaign. 

The Democratic Congressional Campaign Committee (DCCC) has spent more than $460,000 in the race. The pro-Democratic House Majority PAC will likely spend more than $400,000 before the race is done, according to a source, and the pro-Democratic group has chipped in $50,000.

Colbert Busch’s campaign has been boosted by her brother, comedian Stephen Colbert. He headlined fundraisers in Washington, D.C., and New York earlier this month.

Democratic National Committee Chairwoman Debbie Wasserman Schultz (D-Fla.), Maryland Gov. Martin O’Malley (D), a number of senators, including Kirsten GillibrandKirsten Elizabeth GillibrandAmerican women will decide who wins and loses in 2018 elections Dems ponder gender politics of 2020 nominee Calls mount from Dems to give platform to Trump accusers  MORE (D-N.Y.), Dick DurbinRichard (Dick) Joseph DurbinAmerica’s waning commitment to the promise of the First Amendment Senate rejects Trump immigration plan What to watch for in the Senate immigration votes MORE (D-Ill.) and Amy KlobucharAmy Jean KlobucharOvernight Health Care: Trump eases rules on insurance outside ObamaCare | HHS office on religious rights gets 300 complaints in a month | GOP chair eyes opioid bill vote by Memorial Day Overnight Regulation: Trump to take steps to ban bump stocks | Trump eases rules on insurance sold outside of ObamaCare | FCC to officially rescind net neutrality Thursday | Obama EPA chief: Reg rollback won't stand Dems seek reversal of nursing home regulatory rollback MORE (D-Minn.), and more than 30 House Democrats co-hosted the fundraising events. 

Colbert Busch had raised $880,000 to Sanford’s $450,000 as of April 25, a sign of her momentum as well as the national support she’s received.

But strategists say private polling shows a much closer contest than indicated in a widely cited public survey from the Democratic-affiliated Public Policy Polling. It found Colbert Busch with a 9-point lead.

“Things are moving in the right direction but they’re not totally locked down,” another national Democratic strategist watching the race said.

Sanford had once appeared  to be the front-runner in the 1st district, even accounting for the baggage he carried from the extramarital affair that derailed his political career in 2009.

Sanford won the district with 63 percent of the vote in his last gubernatorial campaign. 

Speaker John BoehnerJohn Andrew BoehnerRestoring fiscal sanity requires bipartisan courage GOP congressman slams primary rival for Ryan donations Speculation swirls about Kevin McCarthy’s future MORE (R-Ohio) endorsed the ex-governor after he won the GOP primary, and South Carolina’s congressional delegation was set to hold a D.C. fundraiser for him. 

The trespassing controversy, however, prompted a rapid GOP retreat.

The National Republican Congressional Committee, which was caught off guard by Sanford’s ongoing dispute with his ex-wife, used the news to wash its hands of him. 

Since then, Sanford has been scrambling to defend against the onslaught of Democratic ads. 

House Majority PAC’s latest ad flays him for his marital infidelity. It features a Republican woman from South Carolina who accuses him of betrayal.

“I used to be for Mark Sanford, but not anymore. He skipped town to be with his mistress on Father’s Day. Sanford even asked his wife for permission to have the affair and wasted our taxpayer dollars on himself,” Jennifer Stark says in the ad. 

“I was mortified, angry, embarrassed, betrayed. I’m a Republican, but Mark Sanford just doesn’t share our values.

But Sanford has not been completely abandoned by Republicans, giving him some hope the trespassing charges haven’t dealt his campaign a fatal blow. 

Sen. Rand PaulRandal (Rand) Howard PaulDem wins Kentucky state House seat in district Trump won by 49 points GOP's tax reform bait-and-switch will widen inequality Pentagon budget euphoria could be short-lived MORE (R-Ky.), former Rep. Ron Paul (R-Texas) and the Tea Party-affiliated FreedomWorks have all endorsed him. South Carolina Gov. Nikki Haley (R) is scheduled to headline a Wednesday fundraiser for him. 

“Mark has proven during his time in office that watching out for taxpayers and holding the line on spending are his top priorities,” Rand Paul said Tuesday.

“What we absolutely cannot afford is someone like his opponent, who will be yet another vote for a return to the [Nancy] Pelosi speakership, for disastrous programs like Obamacare, and for more spending and debt.”

In the face of mounting pressure for a Colbert Busch victory, national Democrats note the race should never have been close in the first place.

“This race proves the same pattern that [former Missouri Republican Senate candidate] Todd Akin’s race proved — that in an overwhelmingly Republican district that never should have been competitive, it can be competitive when Republicans nominate weak and flawed candidates,” said Jesse Ferguson, a spokesman for the DCCC. 

“It’s a competitive race where Democrats have overcome an 18-point deficit in the district because of the flaws and the weakness of the Republican nominee, and the strength of a Democratic candidate as a problem-solver.”