Election 2020 updates: Obama, Biden finish day of campaigning in Detroit

With nearly $300 million in total spending pouring in, the North Carolina Senate race has been the most expensive congressional race so far in 2020, followed by Iowa and South Carolina, according to data from the Center for Responsive Politics.

In the 10 most expensive Senate races this year, Democrats have been vastly outraising and outspending Republicans, especially where Democratic challengers are competing against Republican incumbents, the center's analysis of campaign spending records shows. Outside political groups not affiliated with the campaigns have also been driving up the spending.

Across the Senate battleground, North Carolina could possibly be the state that tilts control of the chamber -- reflected in $280 million in both campaign and outside money being poured into the state. The candidates have spent more than $64 million in the contest, with Democrat challenger Cal Cunningham raising and spending more than twice the amount of Republican Sen. Thom Tillis. Outside groups have also spent upward of $215 million supporting the two.

The contest between Republican Sen. Joni Ernst and Democratic challenger Theresa Greenfield in Iowa has also attracted far more spending from political interest groups than the candidates. Outside groups have funneled at least $170 million into the race, with more than $94 million going into unseating the incumbent senator and more than $74 million spent to fend off the challenger. The candidates' campaigns have spent about $64 million combined so far.

South Carolina has spent more than $209 million in a surprisingly competitive race for this cycle. The candidates have spent far more than outside groups in this race, with $164 million being spent by Democrat Jaime Harrison and GOP Sen. Lindsey Graham, compared to $45 million by outside groups. Harrison's campaign had raised $107 million and spent $104 million of that by mid-October, while Graham has raised $72 million and spent $60 million.

-ABC News' Kendall Karson and Soorin Kim

At the second of his four Pennsylvania rallies on Saturday, President Donald Trump railed over a recent Supreme Court ruling allowing absentee ballots in the state to be counted after Election Day in Pennsylvania and North Carolina.

 “I've had many disappointing opinions from the Supreme Court, I will tell you,” Trump said at the rally in Reading. "That was a terrible decision."

He also conflated the likely delay in election results due to the historic increase in mail-in ballots with voter fraud, of which there is very little evidence, and baselessly claimed votes counted after Election Day would be “when the cheating’s gonna take place."

"Do you know when the cheating’s gonna take place? From the third to whatever the date it is that they gave," he said, calling the deadline extension "disappointing."

"That was a very political decision, I have to say," he said.

-ABC News' Will Steakin and Elizabeth Thomas

President Trump's Pennsylvania rally blitz on Saturday is primarily taking him to GOP strongholds to excite supporters and activate Republicans who may not have voted four years ago -- a bid to supercharge Election Day turnout to offset any Democratic gains in the suburbs.

Stop 1: Bucks County 

Bucks County is 25 miles north of Philadelphia and the fourth-most-populous county in the state. It's Trump's only stop on Saturday to an area that isn't reliably Republican. While it's gone blue in every presidential election since 2000, the margin has tightened in recent years. Hillary Clinton won Bucks County by fewer than 3,000 votes in 2016. Demographically, Bucks County is 88.1% white, with 40.5% of residents holding bachelor's degrees or higher, according to the 2019 census. 

Stop 2: Berks County
Trump stopped next in Reading, the seat of Berks County and the fifth-largest city in Pennsylvania. Berks County came close to flipping for former President Barack Obama in 2012, where he lost by under 2,000 votes. Trump closed that gap four years ago, seizing the lion's share of the vote by 18,000. Demographically, Berks County is a little more diverse than Bucks. The census estimates that as of 2019, 86.9% of Berks County residents identified as white and 22.5% identified as Latino -- compared to 5.7% in Bucks County. Only about 24.5% of Berks County residents hold degrees.

Stop 3: Butler County 
Trump will travel next to Butler County in western Pennsylvania, another Republican stronghold since 2000. He handily trounced Clinton here in 2016, receiving more than 61,000 votes compared to Clinton's 26,834. According to The Associated Press, more than 10,000 Republicans in the county did not vote in 2016. Butler County is overwhelmingly white, according to census estimates (95.8%), and only 35.4% of residents hold bachelor's degrees or higher.     

Stop 4: Lycoming County
The final stop will be Montoursville in Lycoming County -- yet another GOP area that has not been hotly contested to as far back as 2000. 

Bonus: Luzerne County
First lady Melania Trump was also heading to Wapwallopen in Luzerne County this evening -- one of three "pivot" counties that went for Trump four years ago after backing Obama twice. 

-ABC News' Benjamin Siegel

Former Vice President Joe Biden tested negative for COVID-19 on Saturday, according to the pool.

This was his 18th negative test announced since Trump's positive diagnosis earlier this month.

-ABC News' John Verhovek