With some races undecided as the US mid-term elections wound down last night, the Democratic Party had seized the House of Representatives from Republicans with 218 seats to 193. The Republicans maintained control of the Senate with 51 to 45 seats.
The house has 435 two-term seats, all of which were in contest, which each represent population-based districts across the country.
Only 35 of 100 of the six-term senate seats were up for grabs, of which there are two in each state.
Democrats also won back many state governor positions from the Republicans' previous majority of 33 out of 50.
University of Otago politics professor Robert Patman said Mr Trump had attacked international organisations such as the United Nations and World Trade Organisation which were crucial to the prosperity of small countries like New Zealand.
The hope would be with greater scrutiny from the house, those attacks may diminish.
''Although he doesn't play by rules, he may feel more constrained and resist from undermining institutions which are important for maintaining our trade and diplomatic interests in the world.''
Some would have expected the Democrats to claw back more power, Prof Patman said.
''It seems as if the Democrats have had quite a lot of opportunities with Mr Trump in the White House.
''My main criticism of the Democrats is they seem to be leaderless.''
There was a high turnout yesterday, partly due to millennials voting in higher numbers.
Mr Trump's success could largely be attributed to a strong economy, his ''zero tolerance'' immigration policy and shrewd manner, Prof Patman said.
However, with control of the house, the Democrats may place more scrutiny on the president.
''What we could expect is a lot more political fire being directed at the White House.''
