What to Expect When Wells Fargo CEO John Stumpf Faces Senate Grilling

— -- Wells Fargo CEO John Stumpf is expected to appear before the Senate Banking Committee today to face questions over allegations that employees of his bank opened or applied for more than 2 million bank accounts or credit cards without customers' knowledge or permission.

It is expected to be the toughest public appearance that Stumpf has made since the scandal was revealed on Sept. 8. Democrats on the committee, led by Sen. Elizabeth Warren, D-Mass., have promised to ask about compensation of senior executives who may be linked to the allegations, among other questions.

Meanwhile, Republicans have also expressed concerns about the allegations.

"I think it’s a question of integrity. A lot of people don’t trust their banks," Committee Chairman Richard Shelby, R-Alabama, told ABC News on the eve of the hearing. "We want to know what went on, why it went on -- was it part of the culture? Was it fostered by conditions? Fraud?"

"I wonder if this is widespread. If it’s widespread, then it’s systemic. We don’t know that yet but it bothers me because it’s not good for business," Shelby said.

The hearing is scheduled to begin at 10 a.m. Here's a guide for what to watch for.

Not Sure What This Is All About? Here's a Short Summary.

1. On Sept. 8, the alleged misconduct was revealed when the Consumer Financial Protection Bureau (CFPB), the Los Angeles City Attorney and the Office of the Comptroller of the Currency (OCC) fined the bank $185 million, saying that more than 2 million bank accounts or credit cards were opened or applied for without customers' knowledge or permission between May 2011 and July 2015. A bank official acknowledged that it had terminated some 5,300 employees, roughly 1 percent of the workforce, in relation to the allegations, and the bank issued a statement saying "we regret and take responsibility for any instances where customers may have received a product that they did not request." Read more.
2. On Sept. 13, the bank announced that it would be ending its controversial employee sales goals program that was at the center of the allegations effective Jan. 1, 2017. According to the Los Angeles City Attorney, employees were opening and funding accounts without customers' permission or knowledge in order to "satisfy sales goals and earn financial rewards under the bank's incentive-compensation program." The CFPB said the bank imposed the goals on its staff because it "sought to distinguish itself in the marketplace as a leader in 'cross-selling' banking products and services to its existing customers." Read more.
3. On Sept. 13, CEO John Stumpf appeared on CNBC, where it was suggested he may need to resign. He said: "I think the best thing I could do right now is lead this company, and lead this company forward."
4. On Sept. 14, it was reported that the FBI and federal prosecutors in New York and California had opened an investigation -- a development that opened the possibility of criminal charges. No charges have been announced yet. Read more.
5. On Sept. 16, the House of Representative's Financial Services Committee opened an investigation into the bank's alleged misconduct as well as "the role of Washington regulators in monitoring and investigating" the alleged misconduct. A letter sent to the bank's general counsel asked him to make four senior executives available for transcribed interviews, including Carrie Tolstedt. Tolstedt, who government filings say is in her mid-50s, was the head of Wells Fargo's community banking division until her retirement was announced in July. The CFPB and OCC did not comment. Read more.
6. Finally, on that same day, Sept. 16, three Utah residents filed what is believed to be the first class-action lawsuit brought by customers against Wells Fargo over the allegations. Wells Fargo declined to comment on the suit, which was filed in U.S. District Court in Utah. Read more.

What to Watch for

1. What Will Stumpf Say?
2. How Will Sen. Warren React and Will Tolstedt Be Singled Out?
All eyes are on Elizabeth Warren to see how she reacts. She already hinted at her outrage last week, when she and four other senators sent a letter to Stumpf asking if the bank planned to "clawback" money it had already paid to executives who might be responsible for the sales practices in question. The letter singled-out Tolstedt in particular, noting that she was "rewarded with more than $20 million in annual bonuses between 2010 and 2015," and that her recent retirement saw her receive "as much as $125 million in stock options and restricted stock shares."
3. Will There Be Further Details on How and Why the Accounts Were Opened?
Until now, all the details we know about the alleged misconduct are from a consent order issued by the Consumer Financial Protection Bureau (CFPB) and press releases from the CFPB and the Los Angeles City Attorney's Office. Of the approximately 5,300 employees who were terminated, we do not know how many were managers and how many were in sales. Additionally, it isn't clear who might have been pressuring the employees to engage in the sales practices in question.

What's Next?

It's hard to predict what will unfold during the hearings. ABC News will have full coverage online and on-air of the major developments.

In announcing its investigation last week, the House of Representative's Financial Services Committee said that it would seek its own hearing. A date for that hearing is not yet known.

A key question is whether Stumpf or any other executive will be forced to step down. An additional question is whether the FBI and federal prosecutors will charge any current or former bank employees or executives.

Developments in the proposed class-action lawsuit (see above) will also be a focus of the scandal, including how many customers come forward to join the proposed class.

Finally, if there are any other lawsuits -- particularly by shareholders or former employees -- they are also expected to make headlines.

Wells Fargo declined to comment ahead of the hearing. The Senate committee will also hear from representatives from the CFPB, OCC and Los Angeles City Attorney's office in a separate panel.

ABC News' Ali Rogin and Ben Siegel in Washington and Rebecca Jarvis and Josh Margolin in New York contributed to this report.