There's a reason Trump said hardly anything about Republican candidate Rick Saccone during a rally in Pennsylvania on Saturday night that was supposed to promote his candidacy.

The reason: Trump thinks Saccone is a terrible, "weak" candidate, according to four sources who've spoken to the president about him.

Trump thinks Saccone is a terrible, "weak" candidate, according to four sources who've spoken to the president about him. Trump held that opinion of Saccone before leaving for the rally, and I've not been able to establish whether his time on the ground with the candidate changed his mind.

Trump isn't the only top Republican who’s found Saccone underwhelming. The widely-held view from Republican officials: Democrat Conor Lamb is a far superior candidate to Saccone and running a far better campaign. Lamb is running effectively as Republican Lite. He's pro-gun and says he personally opposes to abortion (though he supports abortion rights).

who’s found Saccone underwhelming. The widely-held view from Republican officials: Democrat Conor Lamb is a far superior candidate to Saccone and running a far better campaign. Lamb is running effectively as Republican Lite. He's pro-gun and says he personally opposes to abortion (though he supports abortion rights). The thing that most irks senior Republicans involved in the race: Saccone has been a lousy fundraiser. Lamb has outraised Saccone by a staggering margin — nearly 500 percent.

Politico's Alex Isenstadt was first to report that Trump was not impressed with Saccone.

I spoke on Saturday to Corry Bliss, who runs the outside groups linked to Paul Ryan and may have as much as $140 million to spend on the midterm elections.

"The lesson of this race is that campaigns and candidates matter,” Bliss told me. “In this environment, when one campaign out-raises and runs circles around the other, that creates a number of challenges that are tough to overcome."

Saccone thanked Trump in a statement for his appearance: "This administration has already made unprecedented progress on behalf of the American people and I look forward to working with him to continue to deliver on the promises made. I could not have asked for a stronger endorsement of our campaign ahead of the March 13 special election." The election is on Tuesday.

Why this matters: Forecaster Nate Silver tweeted today: "Stating the hopefully-obvious, but the fact that PA-18 is competitive is a really bad sign for Republicans. It voted for Trump by 20 points and Romney by 17. The previous Republican incumbent there (Tim Murphy) didn't even have a Democratic challenger in 2014 or 2016 & won by 28 points the last time he did, in 2012."

Polls suggest a tight race — RealClearPolitics calls the contest a "Toss Up" — and even a narrow victory by Saccone would be a massive swing against Republicans.

Should Saccone lose, Republicans will be quick to describe his loss as meaningless and will argue it's not a bellwether for November's elections. They'll say he was a terrible candidate and that his loss should be a wake-up call to other Republican candidates who may be getting lazy about their fundraising.

Bottom line: Cook Political Report's Amy Walter emailed me this quick analysis: "My short answer is that one should never read too much into any one race but this is more than Saccone. This is a red congressional district that should go for the generic Republican. But the environment today is much worse than 'normal' for Republicans. That’s not because of Saccone or Lamb, but because of Trump."

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