Everyone likes to present political parties as a unified front. But each Senator represents his or her own state, not the entire party. You have to be able, at some point, to go home and get voters to send you back.
Joe Manchin is very much a big spender in the mold of his predecessor, the infamous Robert Byrd. If you're not aware, a lot of West Virginia infrastructure is named after him. Manchin is a Democrat somewhat for the same reason: money for the state. The March 2021 stimulus is a prime example of Manchin very much favoring government spending. From Manchin's own website
West Virginia alone will receive approximately $140 million for broadband expansion, $152 million for emergency rental assistance, and $1.34 billion for our schools and childcare facilities. Every city, town, village and county in the state will receive funding to rebuild our crumbling infrastructure and support essential frontline workers. A vast majority of West Virginians will also receive $1,400 stimulus checks. We were also able to extend unemployment benefits through the end of August and protect those receiving unemployment benefits and making less than $150,000 from being hit with an unexpected tax bill next year. This relief bill will help West Virginia rebuild after this incredibly difficult year.
Shocker of shockers: even Republicans like money. But the proposed major Democratic stimulus after that sparked fears of inflation with Manchin
What I have made clear to the President and Democratic leaders is that spending trillions more on new and expanded government programs, when we can’t even pay for the essential social programs, like Social Security and Medicare, is the definition of fiscal insanity. Suggesting that spending trillions more will not have an impact on inflation ignores the everyday reality that America’s families continue pay an unavoidable inflation tax. Proposing a historic expansion of social programs while ignoring the fact we are not in a recession and that millions of jobs remain open will only feed a dysfunction that could weaken our economic recovery. This is the shared reality we all now face, and it is this reality that must shape the future decisions that we, as elected leaders, must make.
Manchin was right (Apr 2022 numbers hit 8.3%). And Manchin clearly knows his own state (Apr 2022 survey)
57% of West Virginia voters approve of Manchin’s job performance, up from 40% during the first quarter of 2021.
While Manchin has made up ground on the right, he’s angered West Virginia Democrats, 54% of whom now disapprove of him, up from 32% around this time last year. However, he’s also made large gains with independents over that time frame, with an approval rating rising from 31% to 50%.
In other words, Manchin is a rare bird in politics: a member of one political party who draws enough support from the other party to win elections. In fact, he can afford to anger his own party within his home state. Remember, Joe Manchin is all but obliged to vote for Democrats to control the Senate (meaning that if he were removed, the Senate would flip 51-49 for Republicans). Former Clinton strategist James Carville notes why the Democrats need Manchin
“Understand that Joe Manchin is a Roman Catholic Democrat in a state in which not a single county has voted Democrat [for president] since 2008,” Carville said.
“Politics is about choices and he’s up for re-election in 2024. If Manchin runs for re-election, I’ll do everything I can to help him because it’s either going to be Joe Manchin or Marsha Blackburn. It ain’t Joe Manchin or Ed Markey.”
Blackburn is a hard-right Republican from Tennessee, Markey a progressive Democrat from Massachusetts.
In short, you'd rather have someone who at least identifies with your party and carries some of positions, than to nominate some who will carry all of your positions... but can't win. There is no other Democrat in West Virginia who is even remotely popular enough to win a statewide election in a state that is currently considered R+23.