The biggest catalyst for the Trump trade has morphed into the biggest liability, as bank stocks have helped thwart what had been a powerful market rally.

Financial stocks dropped again Monday, with banks specifically off about 1.7 percent around midday as measured by the SPDR S&P Bank exchange-traded fund. It was hardly the first time the sector had been a drag on the market in recent days; the bank ETF is off 7.5 percent over the past month.

In all, it's been a startling turnaround for a group that epitomized what President Donald Trump is hoping to do. His agenda of lower taxes, less regulation and more infrastructure spending, coupled with expected higher interest rates, seems tailor-made for lenders.

However, recent political stumbles have triggered unease over whether Trump will be able to get that agenda through an increasingly hostile Congress.

As a result, bank stocks, which soared as much as 33 percent after the election, have tailed off strongly of late.