Rep. Raúl Grijalva (D-Ariz.), co-chairman of the 90-plus-member Congressional Progressive Caucus, emerged this year as a key player on health care reform as he helped resuscitate the public insurance option after a brutal August town hall season made many Congressional Democrats skittish about the idea.

An earthy, rumpled former social worker and community activist from Tucson who didn’t get a college degree until he was 39, Grijalva seems better suited to talk to House leaders and less liberal colleagues than some of his fellow Congressional progressives, and he has been able to communicate the caucus’ priorities without alienating House leaders and centrist colleagues.

For months, the four-term Member kept 60 or so progressives together in demanding a “robust— public option — one tied to Medicare rates to keep the pressure on private insurers to compete and lower costs. Grijalva was rolled in the end by Speaker Nancy Pelosi (D-Calif.) when she was forced by party moderates to abandon the Medicare-based public option, but other Democrats credited his tough early stand as helping to ensure a public option stayed in the bill at least through House passage.

As a conference with the Senate looms, Grijalva is again rallying liberals to fight any proposals for a “trigger— for the public option, calling it a “back-door attempt to kill the public option and confuse voters.—

“A public option trigger cannot pass the House and will be fought by united voices around the country until it is defeated,— he warned last week. But progressives’ credibility took a hit when they walked away from similar statements about the Medicare-based public option. Either way, Grijalva is one to watch down the stretch, as liberals know they will get even less out of a House-Senate compromise bill but don’t want to lose their best opportunity in a generation to enact sweeping reform.