An upswing in the U.S. economy has contributed to a surge in economic optimism but provided no similar improvement in the standing of the nation’s political leaders, a new Wall Street Journal/NBC News poll shows.

Half the public said the past year brought important economic improvements, a postrecession high, while more than four in 10 said they are satisfied with the state of the economy, the most upbeat reading in more than eight years.

The poll of 800 adults points to a significant mood swing among Americans as the public benefits from dropping fuel prices, increased employment and other signs of economic growth. After decades of pessimism, almost half of Americans say the country isn’t in a state of decline.

“This is a pivotal moment,” said Bill McInturff, the Republican pollster who conducted the survey with Democrat Fred Yang. “We’ve busted out of the great recession.”

But as President Barack Obama prepares to deliver his State of the Union address Tuesday, the survey found he isn’t getting much credit for the economic improvements. And people continue to be deeply frustrated with Washington leadership in both political parties.

Before Mr. Obama delivered last year’s State of the Union, only 28% said they were satisfied with the state of the economy, while 71% said they were dissatisfied. That gap has narrowed to 45%-54%, the latest poll found, marking the survey’s highest level of satisfaction since 2006.

When asked last year if they saw signs the economy was improving, a majority said no, while 42% said yes. Now, the poll found 50% saw real economic improvements in 2014.

And when asked if the country was on the decline, about half said yes and half said no—the most upbeat in at least 25 years.

An expanded version of this report appears on WSJ.com