Trump's election market gains are on the brink of disappearing.

• Since Election Day, the S&P 500's return has decreased to approximately 0.5%.
• Since Barack Obama's inauguration in 2009, it would be the worst performance for the broad index between an election and inauguration up until Inauguration Day on Jan. 20.

The Trump bump could become the Trump slump.

Since Election Day, the return on the broad index has decreased to approximately 0.5%. If this trend continues until Inauguration Day on January 20th, it will mark the poorest performance for the index between an election and inauguration since Barack Obama took office in 2009 during the Global Financial Crisis, according to data from Bespoke Investment Group.

The stock market experienced a significant increase in value after Donald Trump's election, with investors optimistic about the potential for tax cuts and deregulation that would benefit corporations. For instance, the Dow Jones Industrial Average jumped over 1,500 points in the session following Election Day.

The S&P 500 has been declining since the focus has shifted back to inflation and the future path of interest rates. Although there was a one-day gain on the Wednesday after Election Day, the index is actually down more than 1% overall.

The major economic changes that Trump pitched have become more complicated due to indications of sticky inflation and spiking Treasury yields. On Friday, the Bureau of Labor Statistics reported that the economy added 256,000 jobs in December, which was above the Dow Jones estimate of 155,000.

Some on Wall Street and in the Federal Reserve have expressed concern that policymakers' plans for wide-reaching tariffs or tax cuts may contribute to inflation if they are feasible.

"LPL Financial's chief technical strategist, Adam Turnquist, informed clients that President-elect Donald Trump's incoming administration is predicted to implement a pro-growth agenda, less regulatory supervision, and possibly lower taxes. However, some of these policies may negatively affect inflation and the escalating U.S. deficit."