President Trump is telling his supporters to concentrate on the economy — not an investigation into his campaign's relationships with Russian officials that has now expanded to include the president himself, as he acknowledged Friday morning.

It might seem like a sensible tactic. After all, President Bill Clinton remained very popular throughout the investigation that dogged him throughout his second term — in part because the American economy was going all out.

“Despite the phony Witch Hunt going on in America, the economic & jobs numbers are great,” Trump wrote on Twitter Friday morning. “Regulations way down, jobs and enthusiasm way up!”

The problem for Trump is that the economy just might not be doing well enough to rescue him. To be sure, things are not as bad as they were at the beginning of President Barack Obama's first term. Consumers are optimistic and stock prices are at record highs. Wages, though, are improving only slowly, and the overall pace of economic expansion has not shown signs of moving toward Trump's ambitious targets.

Traders have been bidding up the price of stocks since Trump's victory. The Dow Jones industrial average finished Wednesday at yet another record high, above 21,376 points. While prices fell modestly on Thursday, the index is still up 17 percent since Trump won the election on Nov. 8.

Consumers also met Trump's election with enthusiasm. After he won, the monthly survey of consumer sentiment conducted at the University of Michigan jumped more than six points after the election. By January, the reading had attained its highest level since 2004.

Since then, though, consumer's enthusiasm has cooled somewhat. Preliminary results indicate a drop-off of 11 points since June 8. The economy has continued to improve and expand under Trump, but not at the breakneck pace he had promised his supporters.

During the campaign, Trump said gross domestic product would grow as much as 6 percent a year under his policies. The most recent data for the last quarter put the pace at just 1.2 percent on an annual basis.

Typical wages have continued to increase at between 2 percent and 3 percent year over year. In other words, workers are getting  raises — but they are modest ones after accounting for inflation, which was about 1.3 percent last year. So far, wages have not risen any more quickly under Trump than they did throughout much of Obama's presidency.

Likewise, employers are hiring steadily as they have been for several years, but for many, the pace is still frustratingly slow. Last month, U.S. firms added just 138,000 positions to payrolls, fewer than the 180,000 or so that experts had forecast.

Trump has not been successful in implementing the major items on his economic agenda. Republicans in the Senate are still working on a bill to undo the Affordable Care Act, also known as Obamacare, which they have argued would bring down taxes and stimulate the economy. Trump said he would repeal Obamacare on his first day in office.

The White House has yet to produce a detailed proposal for a broader tax cut. Plans to rebuild the country's infrastructure, another one of Trump's main economic priorities, are similarly vague.

That said, the mediocre economy is largely a result of forces beyond Trump's control. In the past, technological progress has made the U.S. economy more productive, allowing American workers to do more with a given amount of equipment and material. That trend has been slowing for years. Meanwhile, baby boomers are aging and retiring, so the country's labor force is not expanding as quickly as it has in the past.

Clinton did not have to overcome those same challenges. The rate of GDP growth averaged 4.5 percent a year during his second term. The economy was doing so well that when he left office, the federal government was operating a surplus.

That data helps explain Clinton's popularity, even after his impeachment.

During his last week in the White House, 66 percent of Americans said they approved of the job he was doing as president, according to Gallup. The polling organization's most recent figure for Trump is just 38 percent.