Dow, S&P 500 edge up, extend all-time closing highs

The upside breakout in U.S. stocks that has catapulted the Dow and S&P 500 stock indexes to record highs slacked off a bit Wednesday as major indexes ended mixed, but the slower pace was still good enough to send the Dow and S&P 500 to new closing highs.

The Dow Jones industrial average, which on Tuesday eclipsed its old high from May 2015, gained another 0.1%, or 24 points, to finish at a new closing high of 18,372.12. Finishing basically flat was the S&P 500, but its tiny 0.01% gain was good enough for a new closing milestone of 2,152.43.

Ending lower was the Nasdaq composite, losing 0.3%. It's about 4% off its July 2015 record high.

On Tuesday, the Dow closed at a record 18,347.65 and the S&P 500 finished at an all-time high of 2152.14.

The U.S. stock market -- which is now enjoying its second-longest bull run ever -- has put together one of its strongest rallies since the start of the bull market back in the spring of 2009. U.S. stocks have shot pretty much straight up ever since the initial sell-off related to Britain's vote to exit the European was viewed as overdone.The hope for more central bank stimulus has helped drive the rally.

Stocks: Second-longest bull market ever still has a lot of kick

While some Wall Street pros say the recent surge has put stocks temporarily in an overbought state, the general consensus is that the bull is alive and well and will post further gains as the breakout continues.

"The new closing high re-confirmed the current bull market that had been stuck at its prior all-time high from May 21, 2015," Paul Hickey, co-founder of Bespoke Investment Group, told clients in a note.

Bespoke research shows that stocks tend to perform well in bull markets after long pauses, like the S&P 500's sideways action over the past 14 months. "The five prior bull markets that experienced such long pauses saw additional gains of anywhere from 20% to 200% once the pause finally ended with another new high," Hickey wrote.

Andrew Adams, a technical analyst at Raymond James, says the stock market's recent breakout to new highs bodes well for additional upside.

"A successful breakout usually results in a strong thrust higher off of the base," he wrote in a report.

European stocks also paused as the broad Stoxx Europe 600 index was fell 0.1%.  Stocks in Japan, Hong Kong and mainland China closed higher.