The winning ticket for bank earnings in the next three months -- and quite possibly future quarters -- is probably in your wallet right now.

While investment banking and mortgage lending were a drag on earnings in the third quarter, some banks saw their credit card businesses perform well as they added clients, tapped retailer partnerships, and had fewer customers unable to pay their bills.

"We issued another 1.3 million credit cards this quarter and active accounts continue to grow," Brian Moynihan, CEO of Bank of America (BAC) - Get Report said on an earnings call last week. "The good news is we are doing it through the lowest cost possible through our core franchise, much lower than other means of growth."

The U.S. economy demonstrated its resilience in the three months through September, with home and auto sales climbing, Wells Fargo CEO John Stumpf said on an earnings call. "The low energy prices that are negatively impacting certain aspects of the economy provided a welcome boost to consumers," he said, "with many now beginning to redirect their savings into purchasing goods and services."

Of course, one quarter's winner can quickly end up being another quarter's laggard, as happened with trading units at JPMorgan Chase (JPM) - Get Report and Goldman Sachs (GS) - Get Report , but there's reason to believe that credit cards could continue to bolster earnings in future quarters. 

Already, they helped banks with Main Street branches such as Bank of America, Wells Fargo (WFC) - Get Report , and Citigroup (C) - Get Report beat analyst estimates in the third quarter. Meanwhile, Goldman Sachsand Morgan Stanley (MS) - Get Report , both primarily Wall Street investment banks without big consumer businesses, posted decisive misses.

"In general, the core banking businesses, with the exception of mortgages, was reasonably strong," said Fred Cannon, an analyst with KBW. Loan growth is consistent with the moderate growth in the U.S. economy, he said.

Delinquencies and write-offs for bad debt at Bank of America, JPMorgan and Citigroup have declined steadily over the past two years, according to data pulled by Ken Usdin's team at Jefferies. Since the third quarter of 2013, Bank of America saw the greatest decrease in net write-offs at 0.49%, while Citigroup and JPMorgan saw decreases of 0.24% and 0.03% respectively.

All of the six biggest banks except Morgan Stanley have outpaced the broader S&P 500 since they began reporting earnings last week, as of Wednesday's close.

Consumer lending may continue to provide a bright spot for finance companies, as lingering uncertainty about when the Federal Reserve will raise interest rates from nearly zero presses on their investment businesses. Banks are trying to take full advantage by expanding partnerships with retailers and finding ways to use merchant and client data to drive sales.

"Credit card balances were up $4 billion, or 14% from a year ago, benefiting from strong new account growth, more active accounts," and the 2014 acquisition of department-store Dillard's portfolio, Wells Fargo CFO John Shrewsberry said on an earnings call. Customers charged $18 billion in purchases in the quarter, up 15% from a year ago, he said.

Similarly, JPMorgan acknowledged opportunities in its card business, despite increased competition in co-branding that caused the bank to reprice renewed deals with United and Southwest Airlines.

"I've spoken my whole life about good expenses and bad expenses," JPMorgan CEO Jamie Dimon said on the call. "We want certain expenses to go up. When we find marketing opportunities in Card, we're going to spend it."

The bank expects to process more than $50 billion in credit-card transactions during 2016 due in part to a product it will introduce next week.