Nearly every one of the Democrats' most vulnerable incumbents split with their party on Friday and voted for a Republican measure to allow Americans to keep their insurance plans under ObamaCare.

All but three of the 26 members of the Democratic Congressional Campaign Committee's Frontline Program — the designation for their most endangered incumbents — voted for the bill.

They joined 16 other Democrats in supporting the measure, which passed the House 261-157. Four Republicans voted against it.

The bill had already picked up four Democratic sponsors: Reps. John BarrowJohn BarrowDem files Ethics complaint on Benghazi panel Barrow thanks staff in farewell speech The best and the worst of the midterms MORE (D-Ga.), Mike McIntyre (D-N.C.), Patrick Murphy (D-Fla.) and Kyrsten Sinema (D-Ariz.). All four are top Republican targets in 2014.

Other vulnerable Democrats voting in favor of the bill include Reps. Carol Shea-Porter (D-N.H.), Nick RahallNick RahallWest Virginia is no longer Clinton country Solution needed: Rail congestion is stifling economic growth Lobbying World MORE (D-W.Va.) and Jim MathesonJim MathesonWork begins on T infrastructure plan New president, new Congress, new opportunity First black GOP woman in Congress wins reelection MORE (D-Utah).

The defections reflect the political realities facing Democrats as the botched rollout of the healthcare law has caused widespread public backlash against the law and the party. Democrats have seen the polling advantage they gained following the government shutdown erased in the wake of issues with the law.

President Obama offered his own administrative fix for the dropped plans on Thursday but failed to fully quiet critics who say his solution doesn't go far enough. The president's solution would allow insurance companies to keep offering current plans until after the midterm elections.

Still, House Democrats had expected the defections on the Upton bill to be far higher.

Vulnerable Reps. Ann KirkpatrickAnn KirkpatrickWomen make little gains in new Congress McCain wins sixth Senate term In Arizona, history and voter registration data gives GOP edge MORE (D-Ariz.), John Tierney (D-Mass.) and Lois Capps (D-Calif.) all voted against the bill.

Republicans are already out hitting them for their votes. The National Republican Congressional Committee issued releases targeting Kirkpatrick and Tierney. One charges Kirkpatrick "broke her promise," a reference to Obama's erroneous pledge that Americans who like their coverage can keep it.

--This post was corrected at 3:15 p.m. to reflect that Kirkpatrick, Tierney and Capps voted aganst the bill.