Former President Donald Trump on Friday pledged to campaign in West Virginia against Sen. Joe Manchin because of the Democrat's $739 billion tax hike and climate change deal. 

Trump said that Manchin and Democratic Sen. Kyrsten Sinema of Arizona, who are both up for reelection in 2024, would pay a heavy political price for agreeing to back the deal after previously withholding their support.

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"What the happened to Manchin and Sinema, what the hell happened, where did this new philosophy come from," Trump said during an address at the Conservative Political Action Conference (CPAC) in Texas. "I think if this deal passes, they will both lose their next election, I do believe that, West Virginia and Arizona will not stand for what they did to them." 

The former president's remarks came as the Senate was debating the massive spending measure. Written by the Democrats, the legislation raises taxes by $739 billion over the next decade. 

Most of the money, nearly $440 billion, is slated to go towards climate change subsidies in hopes of reducing greenhouse gas emissions 40% by 2030. 

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Given widespread GOP opposition, Manchin and Sinema's support for the bill is key because Democrats plan to push it through the 50-50 Senate using a party-line process known as budget reconciliation. 

"Maybe this speech can stop them, because when Manchin hears me say he's going to lose West Virginia," said Trump. "I'll go down [there] and campaign against him as hard as anybody can." 

Democrats have pitched Manchin-Schumer bill as a salve for inflation. They argue it will lower electricity bills through new climate change subsidies and cap the amount of money that elderly Americans pay out of pocket for some life-saving prescription drugs

"It's a bill for America," said Manchin after agreeing to the deal. "We have an opportunity to lower drug costs for seniors, lower [Obamacare] health care premiums, increase our energy security, and invest in energy technologies — all while reducing our national debt."

Trump, who won West Virginia by nearly 40 percentage points in 2020, contended otherwise, saying the bill's tax provisions were a "rip-off." The former president also questioned Manchin's credibility claiming that the West Virginia Democrat had previously flip-flopped on impeachment. 

Manchin points at a reporter

Sen. Joe Manchin, D-W.Va., calls on a reporter during a press conference about Democrats' reconciliation bill.  (Tyler Olson/Fox News)

"I got along with him fantastically well, he called me all the time," said Trump. "When the impeachment hoax started [Manchin] said: ‘I would never vote against you, you’re a great president.'" 

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"Then when we were counting up the numbers … he voted against me," said Trump.