“The whole world ... They're all watching,” President Donald Trump told a Pennsylvania crowd on Saturday ahead of Tuesday's hotly contested House special election taking place in a district that he won by nearly 20 points in 2016.

“This guy should win easily,” Trump said, referring to Republican candidate state Rep. Rick Saccone, who stands as the president's latest attempt at using his political capital to impact congressional races ahead of the 2018 midterms.

Tuesday's special election for Pennsylvania's 18th District ought to be a slam dunk for Republicans. President Trump handily beat out Democratic presidential nominee Hillary Clinton in the 18th District back in 2016 on his way to capturing the Keystone State and subsequently the White House. And the Republican Party and conservative groups are backing up trucks of cash to Saccone.

The Republican candidate has also benefited from outside conservative organizations spending $4.7 million on advertisements leading up to Election Day to ensure the seat held for 15 years by Republican Rep. Tim Murphy stays red.

Who's likely to win? 

The Cook Political Report initially said the race favored Republicans, citing the way Pennsylvania districts were drawn. But recently, Cook changed the race's distinction to being a toss-up — which alone could be viewed as a small victory for Democrat candidate Conor Lamb, who is looking to flip the longtime red seat.

While Saccone has led most polls leading up to Tuesday, recent numbers suggest a blue surge could continue the small pattern of Democratic upsets in red strongholds.

A new Monmouth University Poll released Monday (a day before the election) shows Lamb pulling away slightly, jumping to a 6-point lead ahead of Saccone, 51 percent to 45 percent.

In the same poll last month, Saccone held a small lead above his Democratic opponent — 49 percent to 46 percent — making Lamb's recent support jump a fairly good indicator for Democrats heading into Tuesday.

Impact on Trump's political capital

Trump putting himself out there, throwing his weight behind another Republican candidate in Saccone, is still a big deal, especially for the president himself. He made that clear during Saturday night's rally in Moon Township.

“This is a very important race. Very important,” Trump said.

“I hate to put this pressure on you, Rick, they're all watching,” Trump said Saturday. “I won this district by 22 points. That's a lot. That's why I'm here. Look at all those red hats, Rick.”

For the president, the 18th District marks his latest attempt at strapping the #MAGA movement to another Republican candidate and hoping that the same political movement that catapulted him to the White House will prove to be more than just a flash in the pan and also have an effect on more than just his own candidacy.

Trump went all in last year, backing Republican Senate candidate Roy Moore in the Alabama special election, only for Moore to lose in historic fashion to Democrat Doug Jones.

Not only did the president campaign for Moore, tweet for Moore — but Trump essentially saved Moore's campaign after numerous and detailed sexual assault allegations were leveled against the Republican candidate. When the Republican candidate's campaign was on life support and party leaders were calling for him to drop out, Trump continued to publically back Moore even as the allegations mounted.

After Moore lost, giving Alabama its first Democratic senator in 25 years, Trump lashed out publically, claiming he knew all along that former judge didn't stand a chance.

“I said Roy Moore will not be able to win the General Election,” Trump tweeted after the loss. “I was right! Roy worked hard but the deck was stacked against him!”

Pennsylvania's 18th District is not only the latest test of Trump's political influence, but it's also another chance to gauge Democratic enthusiasm. Opposition parties historically have successful midterms, but some Republicans are doubting the size of the rumored impending blue wave that progressives hope will paint Washington Democrat in November.

Will the 2018 midterms prove to be a Republican purge thanks to a historically unpopular president? Or will Democrats come up short again? Tuesday will be the latest hint at answering both of those questions.