A re-energized US Democratic party claimed both governors' seats up for contention on Tuesday, signaling that the party could make significant gains in next year's midterm election.

Early unofficial results showed that Democrat Ralph Northam defeated his Republican rival Ed Gillespie in Virginia. Meanwhile, in New Jersey, Democrat Phil Murphy swept to victory against Republican Lieutenant Governor Kim Guadagno. Both gubernatorial races were seen as a test of the Trump presidency, which has appeared to be waning in popularity in recent months. Tuesday's results, however, sent a clear message of rebuke at the president.

Read more: Trump isn't on the ballot, but he is on Virginia's mind

Both Northam and Murphy's campaign platforms actively tried to tap into anti-Trump sentiment. In Virginia, a swing state where immigration and Confederate statues proved to be major policy topics, Northam succeeded by tying his Republican opponent to Trump's combative style of politics.

As news broke that he was on course to win the election, Northam tweeted: "Tonight we proved that we're stronger when we value and fight for one another."

In New Jersey, Murphy said he was running for the governorship to act as a check on the president. Murphy, a former investment banker and ambassador to Germany, hammered his Republican rival Guadagno for her association with the deeply unpopular outgoing governor and close Trump ally, Chris Christie.

Riding the wave of rousing dissatisfaction directed at the Trump White House in the Democrat-leaning state, Murphy also promised voters that he would block the president on immigration policies, if he were to win office. Northam and Murphy's election successes mark the first time since Trump's election to the White House that the Democratic Party has been able to translate anti-Trump sentiment into success at the ballot box.

Trump responds to GOP's Virginia defeat

Although Trump did not campaign directly for Gillespie, the president did endorse him and posted a number of tweets and recorded messages in the run-up to the vote. Many of Gillespie's policy proposals, particularly regarding immigration, even closely reflected the president's.

However, immediately following the Republican's defeat, Trump took to Twitter to pin the blame on Gillespie, posting: "Ed Gillespie worked hard but did not embrace me or what I stand for."

Mayor Bill de Blasio wins second term in New York City

Democrats were also celebrating New York City Mayor Bill de Blasio's victory over his Republican opponent, Nicole Malliotakis, on Tuesday. The 56-year-old de Blasio had won nearly 66 percent of the vote with more than 93 percent of votes counted.

His progressively liberal campaign focused on tax hikes for the rich, increasing affordable housing and keeping the city's crime rate low.

First transgender lawmaker wins legislative race

The Virginia elections also saw the first openly transgender person win a state legislature race. Democrat Danica Roem, a transgender woman, was elected to the House of Delegates, replacing the socially conservative Republican incumbent, Bob Marshall.

A former journalist, her key policy issues included jobs, schools and traffic congestion.

amp, dm/kl (AP, Reuters, dpa)