President Donald Trump’s re-election campaign long maintained there were thousands of new supporters tucked into rural, red pockets of the country who would come out and vote for the president when asked.

On election day, there was proof.

With the race unsettled in several key battlegrounds, Mr Trump’s strong election day surge may not be enough to overcome a Democratic operation that also boosted its vote. With votes still being counted, the total turn-out has already surpassed 2016 levels.

But the tight presidential races and unexpected Democratic losses in congressional races demonstrated the resilient power of Mr Trump’s appeal with rural, white voters and a growing polarisation that may outlast his leadership.

William Frey, a demographer with the Brookings Institution, said the Trump campaign strategy was tenuously built on increasing support in places that are losing population, while the Democrats’ relied on groups with growing cities and suburbs.

“The clock is ticking,” Mr Frey said. “But in this election we found it’s not ticking fast enough for the Democrats.”

Even as the winner of the White House was unclear, Republicans had victories to celebrate on Wednesday – and white, rural voters to thank.

In Iowa, Democrats had hoped to pick up a Senate seat, but Mr Trump won the state comfortably on the strength of his rural turn-out, while Republican senator Joni Ernst also held her seat.

Democratic Representative Abby Finkenauer lost her re-election bid in the eastern part of the state as Mr Trump bolstered his margins in rural areas like Buchanan County just west of Dubuque. Mr Trump won the rural county, which is 96% white, by 15 percentage points in 2016. That margin jumped to 21 percentage points this year.

In North Carolina, Mr Trump picked up 2,400 votes over his 2016 total in tiny Columbus County, near the South Carolina border. He repeated that pattern across the state’s vast rural areas, blunting the Democratic surge in its urban base.

Democrats had hoped to win the state outright for Mr Biden and oust Republican senator Thom Tillis as part of their effort to win majority control of that chamber. Both races were too early to call on Wednesday.

Democrats also mobilised their voters to drive what may be historic turn-out levels. Those Democratic voters were more likely to vote early and by mail — meaning their votes were slower to be counted. As the vote counts increased, several key battlegrounds — including Wisconsin and Michigan — became Biden victories and Mr Trump’s leads were narrowing in Pennsylvania and Georgia.

But an Associated Press analysis of results found the strong turn-out — so far — was tilted in Mr Trump’s favour. In counties where vote totals were higher than the last presidential election, Mr Trump increased his margins more than his Democratic opponent did, when compared to 2016 nominee Hillary Clinton’s vote. While the differences were small — an average of 0.2 percentage points — it’s enough to tally up tens of thousands of additional voters.

There were many of these high turn-out areas — the country tallied at least 140 million votes, surpassing the 2016 total. The number is expected to keep growing, especially as California slowly counts millions of additional ballots, a process that can take weeks. Determining the national turn-out rate will take as long or longer.

Experts believe this election could feature the highest turn-out rate — the percentage of the eligible population that votes — since before all women were granted the right to vote in the 20th century.

One of the counties to surpass its 2016 turn-out was Butler County, Pennsylvania, a stretch of suburbs and towns north of Pittsburgh, where Mr Trump won two-thirds of the vote and racked up a 36,000-vote margin in 2016. His margin was a few hundred votes higher this year.

Mr Trump held one of his final, largest campaign rallies in Butler, drawing an estimated 54,000 people two days before Election Day. State Republicans spent months signing up new GOP registrants in the county — the GOP netted 11,000 voters over Democrats since Trump’s 2016 election.