Wall Street is getting even more bullish on stocks

• Oppenheimer has raised its year-end S&P 500 target to 5,900, the second-highest on Wall Street.
• Chief strategist John Stoltzfus says tech leadership will broaden out to other sectors.
• He cited resilience in consumer spending, as well as job and wage growth.

The S&P 500 has already scored more than 30 record highs this year, but Wall Street grows more convinced the index's bull run has further to go.

The latest entry came on Monday, when Oppenheimer lifted its year-end forecast to 5,900 from 5,500, indicating roughly 6% upside from Tuesday's close. The shift makes the firm the second-most-bullish on Wall Street.

"Just like before, it's a matter of the fundamentals, where they stand right now. It includes the resilience of the consumer, even as the economy slows down; quite a bit of resilience there — the resilience in business, job growth, wage growth,"John Stoltzfus, Oppenheimer's chief investment strategist, told CNBC.

His thesis also pushes back on recent concern of an over-concentrated S&P. Just a handful of tech stocks have been doing the heavy lifting for the benchmark index, giving investors pause on how sustainable the current rally is.

But while returns on the seven leading large-caps stocks more than double the rest of the index, Stoltzfus noted that other market sectors have still notched sizable gains since an October trough.

By that measure, the S&P has been broadening out. That shouldn't stop either, Stolztfuz added, citing that investors are less focused on short-term gains and will continue to expand the rally.

"It's driven a lot by intermediate to longer term investors, some of which are just the citizenry recognizes that there's real threats to Social Security stability, and people realize they need to play a role in their own retirement," he said.

It's also possible that the Federal Reserve will implement a rate cut late in the year, boosting stocks higher; but Oppenheimer doesn't share the market's optimism for a September pivot.

Only Evercore's S&P estimate of 6,000 outpaces Oppenheimer's forecast. Among Wall Street's biggest banks, UBS and Goldman Sachs hold the highest outlook at 5,600.

Meanwhile, pessimistic analysts are harder to come by. Last week, Marko Kolanovic — one of the Street's last remaining bears — left JPMorgan.