CREDO super-PAC, a national progressive group, is wading into five competitive Senate races this cycle but has left three of the Democratic Party’s most vulnerable incumbents off its list.

According to a release announcing the group’s plan, “CREDO’s goal is to give progressives a vehicle for saving the Senate without supporting some of the worst Democrats in the tightest races such as Louisiana’s Mary LandrieuMary LandrieuProject Veritas at risk of losing fundraising license in New York, AG warns You want to recall John McCain? Good luck, it will be impossible CNN producer on new O'Keefe video: Voters are 'stupid,' Trump is 'crazy' MORE.”

The group “will skip races in states like Arkansas and Louisiana where the Democratic incumbents frequently vote against progressives,” the release says, but could add Oregon and Iowa to its list of active states if polling shows the Democrats there are vulnerable.

Republicans need to pick up only six seats to regain control of the Senate, and their path to the majority goes directly through those four states won by GOP presidential nominee Mitt Romney but held by a Democrat — only one of which, North Carolina, CREDO plans to engage in.

The super-PAC plans to go on offense in Georgia, where Sen. Saxby ChamblissClarence (Saxby) Saxby ChamblissLobbying World Former GOP senator: Let Dems engage on healthcare bill OPINION: Left-wing politics will be the demise of the Democratic Party MORE’s (R) retirement has opened up a seat Democrats believe they can make competitive with their top-tier recruit, Michelle Nunn, and Kentucky, where Democrats are excited about their chances against GOP Sen. Mitch McConnellAddison (Mitch) Mitchell McConnellGOP strategist donates to Alabama Democrat McConnell names Senate GOP tax conferees Brent Budowsky: A plea to Alabama voters MORE.

They’ll also work to defend an open seat in Michigan, and Democratic Sens. Mark UdallMark UdallDemocratic primary could upend bid for Colorado seat Picking 2018 candidates pits McConnell vs. GOP groups Gorsuch's critics, running out of arguments, falsely scream 'sexist' MORE in Colorado and Kay HaganKay HaganPolitics is purple in North Carolina Democrats can win North Carolina just like Jimmy Carter did in 1976 North Carolina will be a big battleground state in 2020 MORE in North Carolina.

But CREDO has no plans to engage in Arkansas, Louisiana or Alaska, where Sens. Mark PryorMark PryorMedicaid rollback looms for GOP senators in 2020 Cotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm MORE, Mary Landrieu and Mark BegichMark Peter BegichPerez creates advisory team for DNC transition The future of the Arctic 2016’s battle for the Senate: A shifting map MORE, respectively, are considered vulnerable because of the red lean of those states.

Those senators routinely break with their party on hot-button issues like gun control and energy production. While their willingness to defy Democratic orthodoxy is a boon in their reelection fights, as they seek to distance themselves from an unpopular President Obama, it can also be an issue for Democratic groups engaging in races this cycle.

CREDO’s president, Becky Bond, said the group is focused on the Senate in part because of frustration with the White House.

"For progressives, the Senate is a firewall against the Tea Party crazies in the House as well as a White House that has demonstrated a propensity to cave to Republicans on the some of the issues we care about,” she said.