'This is by no means any reason for anybody to panic,' trader Kenny Polcari says

The market may pull back if the Republicans' health-care bill fails to pass, but investors need to keep everything in perspective, trader Kenny Polcari told CNBC on Wednesday.

The vote is expected in the House on Thursday.

"We're only off 2.5 percent off the highs. This is by no means any reason for anybody to panic. Even if we go down another 3 or 4 percent we're not even in correction territory," the director at O'Neil Securities said in an interview with "Closing Bell."

The legislation, which would replace Obamacare, is the first big test for President Donald Trump and congressional Republicans. It's not only facing opposition from Democrats but also from within the Conservative wing of the GOP.

In order to win passage, Republican leaders can't afford to lose more than 22 votes from members of the party's caucus. As of Wednesday afternoon, more than 22 Republicans have indicated they will or likely will vote no on the bill.

That said, Trump is still confident the measure will be approved on Thursday, White House spokesman Sean Spicer said during a news conference on Wednesday.

Polcari said right now investors are assuming the legislation won't pass. Instead, he thinks how much the vote missed by and what members of Congress are saying will dictate the amount of the market pullback.

However, that sell-off will only be temporary, said Ben Mandel, global strategist for JPMorgan Asset Management. Therefore, he sees a buying opportunity.

That's because of three factors right now that are supporting a positive view on equities and other risk assets, he told "Power Lunch" on Wednesday. One is global reflation, which supports corporate profit growth. Two is the business cycle, which is showing a low risk for a recession. Lastly, policy weighs in.

"What you're talking about is removing some of the upside on the policy aspect of it, when the other two are still continuing to fire," he said.

Neil Hennessy, portfolio manager and chief investment officer at Hennessy Funds, isn't putting too much credence on the passing or failing of the health-care bill.

"If it fails tomorrow it's no different than losing your first basketball game of the season. It doesn't mean the season is over," he told "Closing Bell."

However, he thinks the real focus should be corporate taxes, which he hopes heads to the floor of Congress for debate.

"That could really put people to work. The health-care bill is not going to put people to work, so I'm not sure they're right on focusing on that from the beginning," Hennessy said.

— CNBC's Dan Mangan contributed to this report.