(CNN) For someone who talks so much about winning, President Donald Trump is racking up quite the losing streak.

The electoral earthquake in Pennsylvania set to send Democrat Conor Lamb to the House of Representatives from a district Trump won by 20 points in 2016 is sparking new questions about the President's personal political potency.

That's because state Rep. Rick Saccone is not the first GOP candidate during Trump's term to win the President's blessing and promptly lose. Trump-backed candidates Luther Strange, Roy Moore and Ed Gillespie also tanked in Senate and gubernatorial races in Alabama and Virginia.

Those busted endorsements suggest that for all his mystical connection with his base, Trump is not necessarily an asset for GOP candidates in special elections. They may also be a sign that the President will be more of a liability than an asset for Republicans come midterm elections in November.

While some Republicans are in denial over the implications of Tuesday's special election in Pennsylvania's 18th Congressional District, others are concluding that relying on the President in reelection races may not be a sure bet.

"You better be ready and in the end you determine your own fate in these things," Rep. Tom Cole, an Oklahoma Republican, said Wednesday.

Other Republicans heaped blame on Saccone, blasting him as a poor candidate, even though he faced a tough political environment contoured by the President's low approval rating.

"You've got to control your own destiny, and he didn't," said Rep. John Shimkus, a Illinois Republican.

The relative talents of Saccone and Lamb are among many factors -- local, national and demographic -- that help explain Tuesday's voting, which left the Democrat claiming victory with just a few votes left to be counted.

But the unpopularity of the President and the fact that he had traveled to the district Saturday to offer his endorsement, albeit in a typically wild and rambling rally, inevitably mean he's getting his share of criticism.

Trump may have both hurt and helped Saccone. His historically poor approval rating is clearly pulling down all Republican candidates. The chaos in governance that the President is fomenting and his alpha male brand of leadership may also help explain his plummet among white female voters, who can be crucial in suburban areas.

But some Republicans think Saccone may have done even worse had it not been for Trump parachuting in on Saturday, lambasting "Lamb the sham" and inspiring some of his loyal voters to cast ballots.

"It was probably a little bit too little too late," said Shimkus.

Two sources close to the White House told CNN's Jim Acosta that the GOP doesn't see Saccone's loss as a referendum on Trump, describing their candidate in PA-18 as "weak."

"Candidates either run hard or run scared. It was obvious that Saccone decided to run scared," one source said.

GOP wake-up call

Still, Republicans accepted Lamb's win as a wake-up call for November, when the GOP's congressional majorities will be on the line.

It might also concern Trump and his political handlers that his twin message of tax cuts and tariffs -- tailored to the former industrial heartland of Pennsylvania -- couldn't drive Saccone to victory despite his own liabilities.

And there is no escaping the fact that other Trump-backed candidates have also lost.

In November, the President endorsed Virginia gubernatorial candidate Ed Gillespie, who belatedly ran a Trump-style scorched earth campaign that was rather out of character. He also lost.

Trump supporters could point to caveats in each case.

In Alabama, the President defied his own instincts by backing the choice of the GOP hierarchy, Strange, rather than Moore, the most anti-establishment, Trump-like candidate. Then, in his run against Jones, Moore's personal baggage might have doomed him no matter what Trump said.

In Virginia, Gillespie was always running uphill, s ince Trump lost the state to Hillary Clinton in 2016 after it was won twice by President Barack Obama.

Despite his losing streak, Trump may not be a millstone for all Republicans in November -- at least not in races in rural districts.

GOP tacticians, however, will have to carefully target his appearances, as they seek to drive out the Trump base to vote in the knowledge that the polarizing President can also fire up Democratic turnout.

"Some Republicans are going to have to run different races than other Republicans, particularly those in suburban districts where Trump is not popular," said Ford O'Connell, a Republican strategist.

"In some of these other districts, Trump might be a huge asset for you. I don't think there is a one size fits all. I would look at this as more suburban versus not as suburban."

Republicans can also console themselves with the fact that Democrats may struggle to re-create the Lamb prototype. The new congressman held some relatively conservative positions on guns and abortion, for instance, and ran against the establishment of his own party. He did not face a primary, meaning that he could not be tugged to the left in a way that might have alienated moderate conservatives and Trump-voting converts.

Lamb also took pains not to alienate Trump voters.

"I know people voted for the President and voted for me. I thank them for hearing me out," he said Tuesday on CNN's "New Day."

JUST WATCHED Conor Lamb claims victory in PA House race Replay More Videos ... MUST WATCH Conor Lamb claims victory in PA House race 01:06

In some ways, Trump's tarnished record of endorsements mirrors the first-term plight of his predecessor.

Coming off his hope-fueled victory in 2008, Obama soon discovered that his appeal was largely limited to his own races.

He endorsed Jon Corzine in the New Jersey gubernatorial race in 2009, who then lost to Republican Chris Christie in a state Obama had won.

Obama also had his own Virginia disappointment, backing Creigh Deeds for governor, who then lost to Republican Bob McDonnell.

Obama, a magnetic campaigner and singular political personality, was never able to transfer his aura to other Democrats -- and he took a pummeling in midterm elections that cost his party the House and effectively stunted his legislative agenda.

When he was back on the ballot himself, however, his political powers were restored and he won re-election by assembling a coalition similar to the one that had carried him to the White House in 2008.

If Trump's latest reverse previews a rout of Republicans at the polls in November, the President will hope that his own political magnetism and quintessential appeal can help him pull off a similar trick in 2020.