In a speech on the floor of the Senate Tuesday, Manchin declared his intention to vote against the Democratic version and blasted President Obama for a failure to lead on the budget. 

"Why are we doing all this when the most powerful person in these negotiations — our president  — has failed to lead this debate or offer a serious proposal for spending and cuts that he would be willing to fight for?" Manchin said Tuesday.

Both Manchin and McCaskill are among the Senate Democrats caught in the middle in the spending debate and are under continuous attack from Republicans who sense vulnerability in 2012. Both are top GOP targets.

The National Republican Senatorial Committee quickly went after McCaskill and eight other Democrats whose seats are up in 2012 for voting against the House GOP plan. 

“If every Missouri family and small business took the same approach to spending and debt that Claire McCaskillClaire Conner McCaskillLobbying world Dem candidate has Hawley served subpoena at CPAC Annual scorecard ranks GOP environmental efforts far below Dems in 2018 MORE takes with spending their tax dollars, every single one of them would be bankrupt and destitute," NRSC spokesman Chris Bond said after Wednesday's vote.

Another Republican target in 2012 -- Sen. Jon TesterJonathan (Jon) TesterSanders, Ocasio-Cortez back 'end the forever war' pledge Dems wrestle over how to vote on ‘Green New Deal’ White House pleads with Senate GOP on emergency declaration MORE (Mont.) voted in favor of the Senate Democratic plan to cut $4.7 billion Wednesday.

Three Senate Republicans also voted against the House plan Wednesday, arguing the cuts aren't deep enough. Sens. Rand PaulRandal (Rand) Howard PaulThe 25 Republicans who defied Trump on emergency declaration Overnight Defense: Senate rejects border emergency in rebuke to Trump | Acting Pentagon chief grilled on wall funding | Warren confronts chief over war fund budget 12 Republican senators defy Trump on emergency declaration  MORE (Ky.), Mike LeeMichael (Mike) Shumway LeeThe 25 Republicans who defied Trump on emergency declaration Dems prepare next steps after Trump's veto Overnight Defense: Senate rejects border emergency in rebuke to Trump | Acting Pentagon chief grilled on wall funding | Warren confronts chief over war fund budget MORE (Utah) and Jim DeMint (S.C.) all voted "no." 

Along with the five Democrats up for reelection next year, another six Senators who caucus with Democrats voted against the Democratic measure Wednesday. Sens. Kay Hagen (N.C.), Bernie SandersBernard (Bernie) SandersO'Rourke faces pressure from left on 'Medicare for all' O'Rourke says he won't use 'f-word' on campaign trail O'Rourke not planning, but not ruling out big fundraisers MORE (Vt.), Jim Webb (Va.), Michael BennetMichael Farrand BennetNew England Patriots player says he will remain in locker room during anthem next season Press: Which way do Dems go in 2020? Koch-backed group pushes for new limits on Trump's tariff authority MORE (Colo.), Carl LevinCarl Milton LevinListen, learn and lead: Congressional newcomers should leave the extremist tactics at home House Democrats poised to set a dangerous precedent with president’s tax returns The Hill's 12:30 Report — Sponsored by Delta Air Lines — White House to 'temporarily reinstate' Acosta's press pass after judge issues order | Graham to take over Judiciary panel | Hand recount for Florida Senate race MORE (Mich.) and Mark UdallMark Emery UdallDenver Post editorial board says Gardner endorsement was 'mistake' Gardner gets latest Democratic challenge from former state senator Setting the record straight about No Labels MORE (Colo.) also voted "no." 

-Updated at 4:32 p.m.