“It’s hard to figure out what exactly would put a dent on this market,” said Key Private Bank’s McCain. “Things haven’t been going too well but sentiment data has been strong.”

“It’s as if the Energizer Bunny has taken over and we’re just going higher and higher,” he said.

Bond prices, meanwhile, caught a bid as the benchmark 10-year note yield hit its lowest level since the days following the U.S. presidential election. Gold prices also hit their highest level in seven weeks.

“Those two markets are maybe signaling concern” among investors, said Jeff Zipper, managing director of investments at the Private Client Reserve of U.S. Bank. “The [stock] market has been flatlining in the past few days as it waits for some clarity.”

In economic news, job openings hit a record high in April, according to the Job Openings and Labor Turnover Survey (JOLTS), which showed a total of 6.0 million openings.

Craig Bishop, vice president of U.S. fixed income at RBC Wealth Management, said that, while the U.S. economy keeps perking along, inflation is still trailing the Federal Reserve’s desired levels.

“I think there’s some concern in the market that the Fed may be done raising rates after June,” he said. “We all know the Fed is data dependent. Right now, there’s a good chance the Fed holds after the June meeting.

The U.S. central bank is set to meet next week, when it’s widely expected to raise rates.

Overseas, investors prepared for a general election in the United Kingdom set for Thursday. While a vast majority of observers still expect May to emerge victorious on Thursday, a Survation poll published last weekend placed the prime minister’s ruling right-wing Conservative Party ahead by just a single percentage point.

On Tuesday, the pan-European Stoxx 600 dropped 0.67 percent, while the British pound slipped 0.1 percent to $1.289.