Sen. Arlen Specter joined a number of his Democratic colleagues today in signing a letter supporting the inclusion of a public health insurance option in a health care reform bill, according to Specter's Senate office.

The letter, addressed to Majority Leader Harry Reid, reads: "We respectfully ask that you bring for a vote before the full Senate a public health insurance option under budget reconciliation rules."

Specter's support for the public option has ebbed and flowed. On Meet the Press in May right after he switched political parties, host David Gregory asked him, "Would you support health care reform that puts up a government-run public plan to compete with a private plan issued by a private insurance company?" Specter replied, "No."

But then my esteemed predecessor, Josh Drobnyk, wrote on this here blog that only a month later at a rally in DC Specter said he supported the public option.

This morning the Republican after Specter's Senate seat, Pat Toomey, sent him a letter urging Specter NOT to sign the letter in support of the public option.

"I urge you to resist the temptation to join your Democratic colleagues in an effort to ram through this terrible bill in a partisan manner through extraordinary procedural maneuvers," Toomey wrote.

Pennsylvania's junior senator Bob Casey has not yet signed the letter, but his office said he continues to support the public option.

Some news outlets reported this evening that Reid says he will work with Democrats and the White House to craft a public option.