The book on Ron Wyden is that he’s one of the Capitol’s grandest thinkers, with a sprawling range of policy interests matched with wonkish expertise, and eager to work outside the box to put a bipartisan stamp on his many big ideas.  

All of that may be true, but so is this: On Thursday the Oregon Democrat will become the most liberal chairman in the modern history of the Finance Committee, the most powerful panel in the Senate.  

Notwithstanding his many well-publicized feints toward Republicans — on health entitlements reform and tax simplification, trade liberalization and clean energy, foreign surveillance and domestic civil liberties, senatorial secrecy and campaign financing — Wyden remains among the senators most loyal to the mainstream American political left.  

His voting record has earned him a 94 percent annual average support score during his Senate career from Americans for Democratic Action and an 88 percent approval level from the AFL-CIO. He’s voted the way President Barack Obama wanted 97 percent of the time in the past five years, CQ Roll Call’s congressional vote studies found. And he’s stuck with his side on 97 percent of votes that fell mostly along party lines during his 18 years as a senator — a time period when the annual Senate Democratic party unity score was 11 points below that. Max Baucus of Montana, who’s off to China as ambassador after more than eight years with the gavel, was a Democratic centrist by every modern measure. His ADA ratings average only 81 percent over the past three decades. So do his party unity scores, meaning he went against the grain (and, as often as not, his leadership) on 1 out of every 5 votes.  

The most recent Democratic chairman before Baucus, in the early 1990s, was the ideologically unpredictable Daniel Patrick Moynihan of New York. He succeeded the decidedly centrist Lloyd Bentsen of Texas, the last of a string of six consecutive pro-business conservative Southerners who had chaired Finance for the Democrats since the late 19th century. (Furnifold Simmons of North Carolina helped create the progressive income tax in 1913, but that was decades before it became the singular bane of conservatives. Russell Long of Louisiana was instrumental in starting Medicare and shaping the Great Society in the 1960s, but his storied career was always more about accomplishment than ideology.)  

And none of the Republican chairmen along the way has come close, either. The most moderate among them looks to be Bob Packwood of Oregon, who resigned in 1995 because of sexual misconduct. (Wyden was elected as his replacement, leading to the unique situation of successive occupants of the same seat chairing the 200-year-old committee, albeit 19 years apart.)  

The 64-year-old Wyden has also made an extraordinarily swift trip to the chair at the center of the dais; he only won his assignment to Finance in 2005. It’s yet another reminder of how much generational turnover has happened in the Senate in the past decade.  

The question on the minds of every lawmaker, lobbyist and advocate with business before the committee is how Wyden will seek to balance his record as a liberal with his fondness for deal-making. Complicating that mix is his reputation as a policy freelancer willing to make arrangements with the GOP even knowing they complicate his party’s positioning and political strategy. (Exhibit A was his on-again, off-again talks with House Budget Chairman Paul D. Ryan about reinventing Medicare just as the 2012 presidential race was heating up.)  

Wyden’s operational style as chairman, and his prospects for newsworthy legislative successes, may not become clear right away. And they might not really be tested before the midterm elections, when a GOP takeover would require him to hand over the gavel after just 10 months to Orrin G. Hatch of Utah.  

Those two have been collaborating on legislation allowing Obama to finish a trade deal with a dozen Pacific nations that Congress could either accept or reject, but not filibuster or amend. Permission to strike a deal already looks to be getting thwarted by Majority Leader Harry Reid, who has come close to definitively spiking any trade promotion authority bill this year.  

Wyden is similarly ready with a bipartisan opening bid on a tax code rewrite: a package he’s been shopping since 2011, with Indiana Republican Dan Coats, that would lower individual rates, raise more taxes from corporations, create incentives for poor people to save and eliminate many deductions for people and businesses. In a speech in Los Angeles last week, he also made clear he’s wide open to discussing significant revisions in the cause of broadening support — right after the 114th Congress starts.  

He knows as well as anyone that a once-in-a-generation IRS overhaul is not in the offing from this riven Congress in this campaign year. Instead, he’s hoping to score a couple of relatively easy wins in the next couple of months: legislation to extend dozens of tax provisions that expired at the end of last year, and at least another temporary relief from the deep cuts in Medicare reimbursement rates that physicians are facing.  

And after that, Wyden may play against type — sort of. Putting aside his reputation for bold playmaking, he may concentrate on focused patience.  

It’s another skill important to both legislating and basketball, Wyden’s sport since college. And, in that game at least, he knows how to pace himself: He holds the unofficial congressional free-throw record, having once sunk 47 out of 50 in a contest in the House gym.