Washington ? When he was elected president, Barack Obama inherited Harry Reid as the Senate majority leader; the choice was not in his hands.

When the Illinois Democrat was elevated to the White House, Reid inherited Roland Burris as the Senate successor to Obama. Reid almost certainly would have preferred someone else.

But now all three — Obama, Reid and Burris — are linked in a way that poses a challenge for the Democrats in the run-up to the 2010 midterm elections.

The dilemma came into focus last Tuesday night when Obama was speaking at a $2 million Las Vegas fundraiser, designed to fatten Reid’s campaign treasury for next year.

Obama, in his remarks at the Caesars Palace event, celebrated Reid’s humble origins in Searchlight, Nev., and compared his success to that of Sonia Sotomayor, the former Bronx public housing resident Obama had nominated earlier that day to be the first Hispanic on the Supreme Court.

Obama said all their stories show that in America those who are “not born into advantage … can make of our lives what we will.”

But sometimes, especially in the hard world of politics, the path to success is not quite so straightforward. Sometimes, those standing athwart that path demand a payoff.

That is what confronted Burris, another up-from-the-bottom politician, last November when he set his eyes on the Senate seat Obama was vacating.

Illinois’ embattled governor, Rod Blagojevich, was furiously raising money for a third-term bid in 2010, racing to beat an end-of-year deadline after which new fundraising restrictions would go into effect.

In a tape released Tuesday by a federal judge presiding over Blagojevich’s corruption trial, just as Obama was flying west to join Reid, you hear the governor’s brother, Robert, putting the arm on Burris to raise more money.

Before he promises anything, Burris says, “I’m very much interested in trying to replace Obama, OK.”

“You and 1 million other people,” Robert replies, suggesting how expensive this competition may be.

Burris explains his dilemma: “If I put on a fundraiser now … it has so many negative connotations, (including) that Burris is trying to buy an appointment.”

Almost any way he tries to help out the governor, Burris adds, “Rod and I both gonna catch hell.” He runs through the possibilities: “I could give him a check,” or have his partner arrange a fundraiser at Burris’ law firm, using a third person’s name, or become a sponsor of someone else’s event.

Brother Bob says, “I understand your concerns, Roland” — but he just wants to get the money. “I mean if you wanna write a check … or have someone else write checks, that’d be great.”

Nothing is resolved in this conversation. Within weeks, the governor is charged by the U.S. attorney and the FBI, who have been tapping his phone, with flagrantly auctioning off the Senate seat. But before the Legislature can impeach and remove him, he names Burris to the vacancy.

Harry Reid initially bars the door, saying he wants no one from Rod Blagojevich’s tainted hands. But as political pressures mount from other African-Americans, Reid caves — and Obama washes his hands of the whole affair. Burris agrees to testify to the legislative committee weighing impeachment, but somehow fails to recall any of his conversations with brother Bob and denies he offered money to the governor. Only after he has been sworn into the Senate does his memory improve to the point that he recalls being asked to contribute.

But last week, with the tape playing on broadcast networks and all over the Internet, Burris insists that since he never wrote the requested check, he’s done nothing wrong. No foul, no penalty, he says.

The Burris case is now before the Senate ethics committee, which has set no deadline for action. The question is what Reid and Obama will say and do about Burris’ intention to brush all this off and act as if he were entitled to retain his Senate seat.

Republicans — and everybody else — will be watching.

— David Broder is a columnist for Washington Post Writers Group.