Noam Galai/Getty ImagesFor the S&P 500 to sustain gains into 2025, four factors need to align, says LPL Research.LPL Research notes that avoiding a recession and a dovish Fed are crucial for continued stock market growth.Trump's policies could be the deciding factor, as some of his policies could impact markets both negatively and positively.As the stock market wraps up a second straight year of 20% gains, the bar is high for the rally to continue into 2025."Investors will have to grapple with a market pricing in a lot of good news," LPL Research said in a note this week.