Sen. Jeff Merkley, D-Ore., on Tuesday became the most recent in-cycle Democrat to support a letter drafted by Sen. Jeanne Shaheen, D-N.H., urging the Obama administration to extend the enrollment window for Americans to buy coverage under the health care law.

Shaheen’s effort, which already had the support of 10 Senate Democrats, is less dramatic than some other measures being floated — including potential legislation from Sen. Joe Manchin III, D-W.Va., that would delay the individual mandate penalty by a year — and has become an attractive option for moderate Democrats who voted for Obamacare and support it generally but still want to be on the record as backing change.

“I am fully supportive,” Merkley said in a brief interview. “[Shaheen’s] letter focuses primarily on the issue of the national exchange. Oregon has its own exchange. I’m going to call upon the president to extend the window so that … states that are running into difficulties have the full six months envisioned in the law for folks to be able to sign up.”

Both Shaheen and Merkley said that lawmakers are still trying to determine whether the White House can make these changes, if officials are willing to do so, and said there are no definite plans yet to draft a bill to force the administration to expand the enrollment window.