The Republicans held on to the Senate and narrowly survived a number of big individual races, including in Florida. The Democrats now control the lower house for the first time in eight years.
“Tremendous success tonight,” the president tweeted. “Thank you to all!”
Trump was watching the results roll in from the White House, where he spent the day holed up with friends and family.
Democrats seized control of the lower house of Congress in midterm elections. Fox and NBC television networks called the result in the US House of Representatives, while confirming expectations that Trump´s Republicans will retain control of the Senate.
The result upends the balance of power in Washington, where Trump has enjoyed an easy ride from Republican dominance of both houses of Congress since his shock election in 2016.
Democrats will now be able to block legislation and light a fire under Trump´s feet with investigations of his opaque finances and Russian interference in his 2016 election, and possibly push for impeachment.
The verdicts in the House and Senate were based on incomplete results as vote counting continued across the country and some states were still voting in a congressional election cast as an unofficial referendum on Trump.
Giddy predictions by Democrats of a so-called “blue wave” landslide in the House were still premature, even if a majority appeared guaranteed.