New homebuyers may be about to flood the US market for existing homes to lock in the lowest mortgage rates they can. In the past two weeks — since Donald Trump was elected president — mortgage rates jumped alongside other interest rates. This happened as investors raised their expectations for economic growth and inflation, placing their bets on Trump’s plans to spend heavily on infrastructure and cut taxes. The Bankrate.com 30-year national average rate was up from 3.5 percent on Election Day to 3.95 percent on Tuesday, the highest level since December 2015. This is still historically low. “In the short-term, some prospective buyers may rush to lock in their rate and buy now, while others — especially those in higher-priced markets — may be forced to delay as a larger monthly payment outstretches their budget,” Lawrence Yun, the chief economist at the National Association of Realtors, said in a data release on Tuesday. The NAR released its monthly report on existing-home sales, which showed that sales rose at the highest annualized pace in a decade during October. Sales increased by 2 percent at a seasonally adjusted annual rate of 5.60 million, beating economists’ consensus forecast.