Vice President Pence, left, stands with Pennsylvania state Rep. Rick Saccone in Bethel Park, Pa. Republicans are outspending Democrats ahead of the March 13 special election. (Keith Srakocic/AP)

Republican-allied groups have dramatically outspent their Democratic rivals 17-to-1 in the first congressional race of 2018, a special election in Pennsylvania that both parties have cast as a potential bellwether for the November midterms.

Four conservative groups have purchased $4.7 million in television and radio ads to help state Rep. Rick Saccone, their candidate for the Pittsburgh-area seat held until last year by disgraced former GOP congressman Tim Murphy, according to Feb. 2 numbers provided by strategists involved in the race. Democratic groups have spent less than $300,000 on behalf of Conor Lamb, who has waged a single-digit race in a district that voted for President Trump by 19 points in 2016.

Republicans are unlikely to change their strategy for the March 13 special election despite Monday's U.S. Supreme Court decision rejecting a GOP request to delay redrawing congressional lines. That process is likely to increase the number of Democratic House seats in the state, though it is too early to tell what impact it would have in the 18th District previously represented by Murphy.

Republicans are counting on a win in the district to send a strong message to donors, strategists and party faithful as the GOP looks to hold on to its majority: Republicans will raise the money and spend it aggressively.

Democratic outside groups, by contrast, view a victory in the district as a lower priority, given the large number of more vulnerable Republican incumbents they plan to target this fall in their quest to win the House. Democratic strategists also say that the uncertainty around the redistricting process could make any victory short-lived. The winner in March will have to face voters again in November, when new district lines could give Democrats a greater advantage.

Though there are more registered Democrats than Republicans in Pennsylvania, Republicans hold 13 of 18 congressional seats. The Pennsylvania Supreme Court ruled in January that those district lines, which were drawn by Republicans in 2011, "clearly, plainly and palpably" violate the commonwealth's Constitution.

Such explanations offer little comfort to supporters of Lamb, frustrated by the lack of outside support. Weeks before the upset that elected Sen. Doug Jones (D-Ala.), Senate Majority PAC united with Priorities USA to form a super PAC — Highway 31 — devoted entirely to that race. Five weeks before the Pennsylvania vote, there's no sign of a similar coordinated push, with Democratic strategists divided on whether to intervene.

"You have a Republican candidate with a ton of negatives and nobody on the air attacking him," said a frustrated Democrat working with Lamb's campaign. "Meanwhile, you have these PACs trying to drill [Nancy] Pelosi's name into everything, because it's the only play they have."

The House Majority PAC, the largest outside super PAC working to flip Congress to Democratic control, has not purchased any ads in the district, though the group has not ruled out future spending before the March 13 election.

But the Congressional Leadership Fund, a group supporting House Republicans, has dropped $1.7 million through Feb. 2, along with 50 full-time employees knocking on doors to get out the vote.

The National Republican Congressional Committee has spent nearly $2.2 million, compared to more than $250,100 by the Democratic Congressional Campaign Committee. Ending Spending and 45Committee, two super PACs largely funded by the Ricketts family, which owns the Chicago Cubs, has put another $845,000 behind its own ads. End Citizens United, a Democratic PAC, has endorsed Lamb but not yet spent any money on the race.

Lamb has tried to turn the influx in outside spending into a sales pitch to raise more money from individual supporters online in donations of $2,700 or less, an area where he has dominated Saccone. Through Feb. 2, Lamb has spent $861,604 on ads, compared to $91,582 by Saccone. A Web ad that debuted this week asks donors not to let House Speaker Paul D. Ryan (R-Wis.) "buy the next special election," directing them to the liberal crowdfunding site ActBlue.

"We're gonna win this campaign, [but] not through big money, not through dark money," Lamb told volunteers at a meet-and-greet in December. "We will never win that race against Republicans, and I think it's time for us to stop trying."

Republican strategists working on the race say they have been surprised by the lack of Democratic money on television. They started the year worried that Lamb would bring significant advantages, as a fresh face and able campaigner, that could set a negative tone for the November midterms.

"I watched 30 seconds of Rick Saccone on video and I watched 30 seconds of Conor Lamb on video, and I quickly decided this would be a race," said Corry Bliss, the executive director of the Congressional Leadership Fund. "We wanted to engage early and help define this race and make it a referendum on Nancy Pelosi."

Republican ads have hammered two themes likely to be repeated across the country — vilifying Pelosi (D-Calif.), the House minority leader, and promoting the Republican tax cut.

"The Trump Administration's bold agenda is delivering results already right here Western Pennsylvania," Saccone said at a Friday rally headlined by Vice President Pence. "Thanks to the [tax cut], it seems like every day, another business is announcing that they're giving bonuses and raises."

Other Republicans say they are hoping a win for Saccone will encourage major Republican donors to increase their spending on congressional elections this fall. "You spend money now, and if you succeed, you get a windfall later," said one Republican strategist. "It's more valuable to spend now and win than it is to be penny-wise and pound-foolish."

Ads from both the CLF and NRCC follow the same theme, using Lamb's last name to portray livestock following Pelosi wherever she goes.

Lamb, like every Democrat currently serving in Congress, opposed the Tax Cuts and Jobs Act; his stated reason, expressed at several rallies, was that it handed "a trillion dollars to the one percent and corporations," threatening the future solvency of Medicare and Social Security.

Yet Republicans have done less with Lamb's quotes than with Pelosi's. "Conor Lamb believed #taxreform was a 'complete betrayal of the middle class,'" Saccone tweeted on Sunday. "Nancy Pelosi referred to the bonuses and wage increases as 'crumbs … so pathetic.' — I think @Best buy giving bonuses, with four stores in #PA18 is a HUGE win for the people!"

Lamb says he does not support Pelosi as the Democratic leader in the House, and would not support her for speaker if Democrats win control of Congress this fall. Rep. Tim Ryan (D-Ohio), who waged an unsuccessful leadership campaign against Pelosi, has sent a fundraising letter on Lamb's behalf; Rep. Joe Kennedy III (D-Mass.) made a campaign stop in the district last week, following his response to the State of the Union. Local Democrats also expect former vice president Joe Biden to visit the district.

Democrats need a net gain of 24 seats to reclaim the majority.

The cash-strapped Democratic National Committee, which spent millions and sent staff to help Democrat Jon Ossoff's unsuccessful bid for a House seat in suburban Atlanta last year, has made no special commitment to Lamb's race. As of Monday, its Pennsylvania investments were limited to the monthly Every Zip Code Counts grants of $10,000 for every state party, and a special innovation grant that went to 11 states total.

The March special election is the result of Murphy's resignation last fall. Murphy, an opponent of abortion, stepped down after a news report claimed the married Republican had asked a woman with whom he had an extramarital affair to get an abortion.

Linda Andrews, who heads Washington County's Democratic Party, said that Lamb and party volunteers had focused on voter-to-voter conversations to rebut the attacks. "Once you meet him," she said, "you understand that the ads are so far removed from who he is."

Local unions also plan a major push for Lamb over the coming weeks, with volunteers manning phone banks, knocking on doors, and talking worker-to-worker in the heavily union district.

"There is a lot of excitement about the race back in the district," said Rick Bloomingdale, the president of the Pennsylvania AFL-CIO. "Every time we have called a meeting we have gotten two or three times what we have expected."