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 Big Dem names show little interest in Senate Gillibrand, Grassley reintroduce campus sexual assault bill 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) TesterOvernight Defense: Trump officials say efforts to deter Iran are working | Trump taps new Air Force secretary | House panel passes defense bill that limits border wall funds GOP angst grows amid Trump trade war Overnight Defense — Presented by Huntington Ingalls Industries — Pentagon approves transfer of .5B to border wall | Dems blast move | House Dem pushes Pelosi to sue over Trump's Yemen veto 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 PaulGOP presses Trump to make a deal on spending House Freedom Caucus votes to condemn Amash's impeachment comments Bolton emerges as flashpoint in GOP debate on Iran MORE (Ky.), Mike LeeMichael (Mike) Shumway LeeHillicon Valley: Google delays cutting off Huawei | GOP senators split over breaking up big tech | Report finds DNC lagging behind RNC on cybersecurity GOP senators split over antitrust remedies for big tech Fix the climate with smaller families 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 SandersBernie SandersIraq War looms over Trump battle with Iran 2020 Dems break political taboos by endorsing litmus tests Iowa Democrats brace for caucus turnout surge MORE (Vt.), Jim Webb (Va.), Michael BennetMichael Farrand BennetThe Hill's Morning Report - White House, Congress: Urgency of now around budget Overnight Energy: Warren wants Dems to hold climate-focused debate | Klobuchar joins candidates rejecting fossil fuel money | 2020 contender Bennet offers climate plan CNN announces four more town halls featuring 2020 Dems 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.