The pressure on the Susan G. Komen For The Cure Foundation to reverse its decision to cut funding to Planned Parenthood for breast cancer screenings for poor people — a decision which has caused an uproar among women’s groups and on social media — is about to get significantly more intense. Nearly two dozen Senators are set to enter the fray.

I’m told that 22 Dem Senators have signed on to a toughly worded letter urging Komen to reverse its decision, which Komen has justified by citing a new rule prohibiting it from funding any group under investigation by the government. (This has conferred legitimacy and signficance on the probe into Planned Parenthood that has been launched by anti-abortion GOP Rep. Cliff Stearns of Florida.)

That’s a significant number of Senators for a letter of this nature, and it makes it more likely that this fight will escalate in a huge way, if Republican Senators begin speaking out in defense of the decision, as David Vitter has. More signatories are likely.

Raising the stakes, the letter — which was spearheaded by Senator Frank Lautenberg — explicitly raises the possibility of “thousands” of women losing access to “potentially life-saving screenings because of a politically motivated attack.” Here’s the letter to Komen’s Nancy Brinker, sent over by a Senate source:

Dear Ambassador Brinker,

We write to express our disappointment with Susan G. Komen for the Cure’s decision to cut funding for breast cancer prevention, screening, and education at Planned Parenthood health centers. This troubling decision threatens to reduce access to necessary, life-saving services. We urge Komen to reconsider its decision.

Planned Parenthood is a trusted provider of health care for women and men. More than 90 percent of the services provided by Planned Parenthood are primary and preventative including wellness exams and cancers screenings that save lives. Each year, Planned Parenthood health clinics provide 750,000 breast exams, 770,000 pap tests and nearly 4 million tests and treatments for sexually transmitted diseases. Twenty percent of all women in the U.S. have visited a Planned Parenthood health center.

For the past five years, grants to local affiliates of Planned Parenthood have been an important part of Planned Parenthood’s work to protect women from breast cancer. Komen funding for Planned Parenthood has provided nearly 170,000 clinical breast exams and resulted in 6,400 referrals for mammograms. In 2011 alone, grants from Komen provided Planned Parenthood with roughly $650,000 in funding for breast cancer prevention, screening, and education. According to a recent statement by Komen, “In some areas of the U.S., our affiliates have determined a Planned Parenthood clinic to be the best or only local place where women can receive breast health care.”

It would be tragic if any woman —let alone thousands of women — lost access to these potentially life-saving screenings because of a politically motivated attack.

We earnestly hope that you will put women’s health before partisan politics and reconsider this decision for the sake of the women who depend on both your organizations for access to the health care they need.

The letter is signed by Senators Lautenberg, Murray, Mikulski, Boxer, Cantwell, Gillibrand, Menendez, Wyden, Blumenthal, Shaheen, Begich, merkley, Tester, Akaka, Sanders, (Sherrod) Brown, Leahy, Baucus, Cardin, Feinstein, Franken, and Kerry.

That relatively conservative senators like Begich and Tester signed the letter is testament to how broad the opposition to this decision has really become.

More soon...

UPDATE: The total number of signatories is now 26; the new additions include senators McCaskill, Stabenow, Coons, and Bingaman.

More on this topic:

Petri: Komen picks politics over health

Dvorak: Komen, Va. Senate bullying women

Wonkblog: The woman behind Komen’s decision