After rallying more than any other sector after the election, banks appeared to be most vulnerable to a pull back based on concerns about the Trump agenda.

The S&P Financial index <.SPSY>, which includes insurance companies as well as banks, fell as much as 2.3 percent with Morgan Stanley (>> Morgan Stanley) its biggest percentage decliner.

The S&P bank subsector index <.SPXBK> fell as much as 2.5 percent on Monday after falling 5.9 percent in the last 6 sessions as it became increasingly clear Trump was struggling to gain support in his own party for his proposal to repeal President Barack Obama's Affordable Care Act.

The S&P bank sector rose as much as 34.8 percent after the election as investors bet it would benefit hugely from lower taxes, lighter regulation and economic growth under Trump.

The President promised to focus on tax reform after the Republicans pulled their healthcare bill on Friday. While tax reform would help banks, investors were not confident Trump would succeed in delivering it.

"The prevailing view is that it may be difficult to get any of the changes done," said Brian Kleinhanzl, an analyst covering banks at Keefe, Bruyette & Woods in New York.

Even if tax reform happens, the concern is that it might be a watered down version of the massive tax cuts Trump promised.

"The potential to get tax reform done sooner is positive. But there's concern about the potential impact because you might have to bring the Democrats along. You might have to make it less impactful. You might not get as low a rate as you wanted," said KBW's Kleinhanzl.

The KBW Regional banking index <.KRX> faced a steeper decline than bigger banks on Monday as investors worried about prospects for loan growth amid policy uncertainty. After falling as much as 3.4 percent the index was last down 1.5 percent.

Shares in Morgan Stanley, which was downgraded to a sell rating by Compass Point on Monday, fell 3 percent to $41.12. It had risen as much as 38.8 percent in the post election rally.

The S&P bank index pared losses but was still down 0.7 percent in late morning trade. Its biggest percentage decliner was Huntington Bancshares (>> Huntington Bancshares Incorporated),down 2.1 percent. The broader S&P financial sector was last down 0.8 percent.

The S&P 500 index was down 0.3 percent on Monday.

(Reporting By Sinead Carew; Editing by Andrew Hay)

Stocks treated in this article : Huntington Bancshares Incorporated, Morgan Stanley