West Virginia Gov. Jim Justice announced Thursday night in a rally with President Trump that he is becoming a Republican because "the Democrats walked away from me."

Justice, a billionaire coal and real estate tycoon, positioned himself as an ally of Trump who inspired him to switch parties.

"I can tell you, this man and myself are not politicians," Justice said, after being introduced on stage by Trump at the rally in Huntington, W.V. "We ran to get something done. We ran and gave up a part of our lives. We ran because we want nothing."

Justice, one of the few remaining Democratic governors, was lightly booed upon entering the stage, but cheered after announcing his party switch.

"Today I tell you I can't help you anymore being a Democratic governor," Justice said. "Tomorrow, I will be changing my registration to Republican."

Justice said he's met with Trump twice in the Oval Office since he became president. The president described Justice as a friend.

"Having Big Jim as a Republican is such an honor," Trump said. "He showed the country that our agenda rises above Left or Right."

Sen. Joe Manchin, D-W.Va., who is up for re-election in 2018, said he is "disappointed" by Justice's decision.

"I have been and always will be a proud West Virginia Democrat," Manchin said in a statement. "I am disappointed by Governor Justice's decision to switch parties. While I do not agree with his decision, I have always said that I will work with anyone, no matter their political affiliation, to do what is best for the people of West Virginia."

On the day news broke that Special Counsel Robert Mueller has impaneled a grand jury to look into Russia's interference in the 2016 election, Justice said the public should focus more on Trump's agenda.

"What in the world is wrong with us as peoples?" Justice said. "Have we not heard enough about the Russians? I mean, to our God in heaven above, think about it. The stock market is at 22,000. And this country has hope and we are on our way."

Justice even poked fun at Trump's former chief of staff Reince Priebus, who the president replaced last week with John Kelly, a retired Marine general and former secretary of Homeland Security.

"You know what else is unbelievable?" Justice said. "This man now has a chief of staff that all of us can pronounce his first name. You know what this name is today: sir."

Justice took over the West Virginia governorship in January after winning by about 6 percentage points last November over his Republican opponent. He declined to endorse 2016 Democratic presidential nominee Hillary Clinton.

The Democratic Governors Association criticized Justice for switching parties so early in his term.

"Jim Justice deceived the voters of West Virginia when he ran as a Democrat eight months ago," said DGA Executive Director Elizabeth Pearson in a statement. "West Virginians have learned that they simply can't trust Jim Justice. He will always put his financial interests above the needs of West Virginians."

A former Republican and independent, Justice's switch back to the GOP increases the number of Republican governors to 34, while the number of Democratic governors falls to 15. Alaska's Bill Walker is the lone independent governor.