Two more members of the Blue Dog Coalition, a group of fiscally conservative House Democrats, lost their primaries in Pennsylvania on Tuesday night, the latest worrisome sign for the group.

Rep. Tim Holden (D-Pa.) lost his primary in a newly drawn district to a more liberal Democrat, while Rep. Jason Altmire (D-Pa.) lost to Rep. Mark Critz (D-Pa.), largely because of union anger at Altmire.

Their losses are the latest problem for the group, which saw its membership shrink from 54 members before the 2010 election to 25 current members. Many of those members are retiring or are in tough races again this year, making it unlikely the group will bounce back to its previous numbers anytime soon.

"I regret that two of my friends and colleagues in the Blue Dog Coalition, Jason Altmire and Tim Holden, will not be returning to Congress next year. Congress needs more independent-minded members like Jason and Tim who are willing to reach across the aisle and find bipartisan solutions to our country’s many challenges," Rep. Mike Ross (D-Ark.), a co-chairman of the group, said in a statement to The Hill. "Redistricting and a broken, polarized Congress have made it tough to be a moderate in Congress. However, I remain confident that the American people want common-sense leadership over partisanship."

Ross is retiring after this term.

Altmire's and Holden's defeats leave 23 Blue Dogs who could theoretically win next election or be replaced by likeminded Democrats. But five are retiring, including Ross, and all of those are in Republican-leaning seats that will be hard for Democrats of any stripe to win. Five more members are facing tough races: Reps. John BarrowJohn Jenkins BarrowOur democracy can’t afford to cut legal aid services from the budget Dem files Ethics complaint on Benghazi panel Barrow thanks staff in farewell speech MORE (D-Ga.), Leonard Boswell (D-Iowa), Mike McIntyre (D-N.C.), Jim MathesonJim MathesonTrump's budget targets affordable, reliable power Work begins on T infrastructure plan New president, new Congress, new opportunity MORE (D-Utah) and Larry Kissell (D-N.C.), who recently joined the group.

The group does have some chances to shore up its numbers: Former Rep. Ann KirkpatrickAnn KirkpatrickHouse Dems highlight promising new candidates Vulnerable House incumbents build up war chests Cook Political Report shifts 11 House races towards Democrats MORE (D-Ariz.), who was in the Blue Dog Coalition, looks likely to win her race, and there are a handful of seats where conservative Democrats have a fighting chance. But those races are unlikely to outweigh their losses.

Ross told The Hill that he was confident the Blue Dogs would be able to expand on their numbers after this election and said their message reflected what most Americans thought on the issues, but admitted that the group faces some serious structural disadvantages, especially in a redisricting year.

"The Blue Dogs are in the middle and we’re used to being attacked from both sides," he said. "While our membership roster may vary from Congress to Congress, our messages of fiscal responsibility, bipartisanship and common sense will always endure and will continue to resonate with the American people."

This post was updated at 11:54 p.m.