Republican Rick Saccone pledges to be Trump's 'wingman' as voters head to polls in tight Pennsylvania congressional race

The race in the Republican-leaning district outside Pittsburgh has become surprisingly competitive

Republican Rick Saccone acknowledges the crowd during a campaign rally with President Donald Trump (AP)

Republican Rick Saccone has pledged to be Trump’s ‘wingman’ as voters head to the polls in a tight congressional race in Pennsylvania.

The race outside of Pittsburgh has become surprisingly competitive, with both Democrats and Republicans pulling out all the stops in the district that Mr Trump won by 20 percentage points in 2016.

Mr Saccone said he’s not surprised the race against Democrat Conor Lamb is so close. Democrats are “throwing everything they can at this race” because it’s a rare open seat, the 60-year-old state lawmaker said.

Despite being a political novice, the 33-year-old Lamb has far outpaced Mr Saccone in fundraising.

Up until last year, the seat in the heart of steel country was occupied by former Republican Representative Tim Murphy, who resigned in October amid a sex scandal.

But while the southwestern Pennsylvania district is Republican-leaning, Mr Saccone has struggled to win the same support that Mr Murphy managed during his 14-year career as a member of US Congress.

Several senior administration officials, as well as Mr Trump and his eldest son Donald Trump Jr, have appeared with Mr Saccone on the campaign trail, attempting to fend off the threat from Mr Lamb.

In an Election Day interview, Mr Saccone told Fox Business Network that the President is “getting beat up in Washington” by the media, bureaucrats and Hollywood. He “needs a good wingman”, the state lawmaker said.

While Mr Saccone has tied himself to Mr Trump, Mr Lamb asserted that the race “didn’t have much to do with President Trump”, according to the Associated Press.

Appearing to recognise that Mr Trump still remains generally popular in the district, Mr Lamb has downplayed his opposition to the Republican president, insisting instead that the race hinges on local issues.

The 33-year-old Marine veteran and former federal prosecutor has positioned himself as a moderate with an independent streak, unbeholden to establishment Democrats like House Minority Leader Nancy Pelosi.

While he has blasted the Republican tax law passed last year – labelling it as a giveaway to corporations at the certain future expense of the US’s fiscal security – he has departed from members of his party on guns. He has said he doesn’t support proposals by fellow Democrats to ban certain weapons, saying that Congress should emphasize enforcing existing regulations.

Mr Saccone, meanwhile, supports Mr Trump’s tax cuts and said he would fight for lower taxes, lower spending and fewer regulations on private businesses. He also opposes many of the federal government’s recent gun-control proposals, including raising the age limit for purchasing certain types of guns from 18 to 21.

The battle between Mr Saccone and Mr Lamb is being seen as a marker for the chances of both Republicans and Democrats in the midterms elections in November.

Democrats are on a mission to recapture a majority in the House of Representatives later this year. Democrats must flip 24 Republican-held seats to take control of the lower chamber, and an upset in Pennsylvania on Tuesday will only embolden them as they look to win in places where the party has lost ground in recent decades.

Inside the White House, aides have reportedly dismissed suggestions that the contest is a referendum on Mr Trump’s presidency, according to the Washington Post.

Along with holding a rally in the area over the weekend, Mr Trump has weighed in on Twitter, writing that Mr Saccone will “be much better for steel and business”.

“The Economy is raging, at an all time high, and is set to get even better,” he tweeted. “Jobs and wages up. Vote for Rick Saccone and keep it going!”

The president of the AFL-CIO, Richard Trumka, who once flirted with an alliance with Mr Trump, also weighed in on the race – but on behalf of Mr Lamb.

Mr Trumka told union voters that the Democratic candidate “supported our agenda” so “now it’s time to ... support him.”

The labour vote is expected to a key factor in determining whether Mr Lamb can pull out a win over Mr Saccone. The AFL-CIO estimates the total union household vote in the district to be 87,000 – about one-fifth of the registered electorate.

The seat’s former occupant, Mr Murphy, had enjoyed union backing, but unions have now lined up behind the Mr Lamb as the candidate has highlighted his Republican opponent’s anti-labour record at the statehouse.