US Republicans have sounded the alarm after Democrats claimed victory in a Pennsylvania congressional election seen as a referendum on President Donald Trump's performance.
Moderate Democrat Conor Lamb claimed victory in the election that should have been a shoo-in for Republicans in a district that Mr Trump won by almost 20 points in 2016.
He campaigned for Republican Rick Saccone, who started the race well ahead of Mr Lamb.
The Republicans are 5-0 in recent Congressional races, a point which the Fake News Media continuously fails to mention. I backed and campaigned for all of the winners. They give me credit for one. Hopefully, Rick Saccone will be another big win on Tuesday.
— Donald J. Trump (@realDonaldTrump) March 11, 2018
Mr Lamb leads Mr Saccone by a small margin and the earliest the election result could be certified is 26 March, according to a state official, but the final tally could be unknown for weeks.
County officials are expected to begin counting provisional paper ballots late this week, and military ballots next week,officials said.
Republicans have until the results are officially certified to challenge the outcome or pursue a recount.
Mr Saccone sent a fundraising email to supporters yesterday saying the "campaign is far from over."
Republican Speaker Paul Ryan called the election a "wake-up call" in a meeting with Republican House members and pushed them to raise more campaign funds.
He also urged them to do more to highlight tax cuts approved by the Republican-dominated Congress and signed by Mr Trump.
However, despite his success this week, Mr Lamb may soon have to start campaigning again - in a different district against a different opponent for the November congressional elections.
This is because the 18th District, as currently drawn in southwestern Pennsylvania, will cease to exist because of a recent court order that set new boundaries for every district in the state.
Mr Lamb, who appeared to have a small but insurmountable lead in the special election for the US House of Representatives seat, likely will start campaigning in the new 17th District.
Republican Rick Saccone, should he still have a political future after apparently failing to win what had been a safe Republican district, might try for the seat in the newly drawn 14th District.
The political game of musical chairs could once again make western Pennsylvania hard-fought ground.
Districts that were once considered solidly Republican and that voted for Mr Trump in 2016 now look winnable by Democrats.
Pennsylvania's top court ruled in January that the state had been unfairly gerrymandered by Republican legislators, with districts shaped in order to include voters apt to favor their party.
Pennsylvania Republicans, including eight US congressmen, have filed a federal lawsuit challenging the new map.
Mr Saccone, a conservative four-term state representative from Elizabeth Township, lives in the newly drawn 18th District that will lean Democratic because it includes the strongly Democratic city of Pittsburgh.
But Mr Saccone has already said he intends to run in the new 14th District, which will include much of the current 18th and strongly Republican communities to the west of it.
Political analysts label the new 14th District safely Republican.
It has a higher share of people who have not studied past secondary school and its median household income, at about $55,000, is lower than the old 18th District's $65,000, according to analysis by PlanScore.
Mr Saccone might want to move to the new district, although Pennsylvania law does not require candidates to run in the districts where they live.
Mr Lamb has not said which seat he would seek in November but was clear during the campaign that he intended to compete.
