Barack Obama is about to create one of the most attractive vacancies in American politics.

And two of U.S. House’s leading progressive members would like to fill it.

The president-elect has announced that he will quit Sunday as Illinois’ junior senator, creating an opening for the seat he has held for a little less than four years. Though he says that serving in the Senate was “one of the highest honors and privileges” of his life, Obama explained in a written statement that he’s ready to begin “the hard task of fulfilling the simple hopes and common dreams of all Americans as our nation’s next president.”

Illinois Governor Rod Blagojevich, a controversial Democrat whose own approval ratings are a good deal lower than Obama’s, can appoint any Illinoisan who is 30 years old to replace the state’s exiting senator. Blagojevich’s pick will serve the remainder of Obama’s term — a little over two years — but must face the voters of Illinois in 2010 if he or she wants a full six-year term.

Illinois Congressman Jesse Jackson Jr., the son of the veteran civil rights leader and former presidential candidate, is seen by some as a frontrunner in the contest. A congressman for more than a decade, he was an early and energetic backer of Obama’s presidential run and delivered an impressive speech on the senator’s behalf at last summer’s Democratic National Convention in Denver. At 43, he would be the youngest member of the Senate if appointed, yet after 13 years in the House he would come to the upper chamber with more legislative experience than did his predecessor.

Jackson’s been a stalwart progressive since his election to the House, as is another top contender for the seat, Illinois Congresswoman Jan Schakowsky. Both have been consistent critics of the war in Iraq, defenders of civil liberties and proponents of presidential accountability.

Even after House Speaker Nancy Pelosi declared impeachment was “off the table,” both Jackson and Schakowsky continued to utter the “i” word and Schakowsky was an early proponent of proposals to impeach Vice President Dick Cheney.

Jackson and Schakowsky have been actively involved in efforts to move the Congress and the Democratic Party toward more populist stances on economic issues, such a trade policy. And both have records of challenging the political status quo. Jackson authored a groundbreaking book, A More Perfect Union: Advancing New American Rights, on constitutional reform. Schakowsky was one of the first members of the House to go after Blackwater, the Iraq contractor, and has appeared with Jeremy Scahill, the author of Blackwater: The Rise of the World’s Most Powerful Mercenary Army.

In the race to replace Obama, Jackson’s won the endorsement of the Chicago Defender newspaper, a historic print champion of African-American advancement. And he has emerged as something of a favorite among members of Chicago’s large black community and many white progressives who think it is important that the only Senate seat held by an African American go to another African American.

There is also some sentiment for Congressman Danny Davis, an lomng-time activist in Chicago’s African-American community who was a key ally of former Mayor Harold Washington and who has received support from a group of elected officials in the city. (David, like Jackson and Schakowsky, is a member of the Congressional Progressive Caucus.) Outgoing Illinois Senate President Emil Jones, a mentor to Obama during the president-elect’s days as a state senator, is another prospect — although, at 73, Jones is a bit older than John McCain and thus is not seem by many as a long-term pick.

Illinois Attorney General Lisa Madigan, a bright and popular young official who has clashed with the governor on ethics issues, also shows up on some lists. So, too, does Iraq war veteran Tammy Duckworth, a political associate of Obama chief-of-staff Rahm Emanuel. Duckworth, a former congressional candidate and head of the Illinois Department of Veterans’ Affairs, is seen by some as a more likely member of an Obama administration — perhaps as chief of the federal Veterans’ Administration.

Obama adviser Valerie Jarrett, a Chicago political insider, has taken herself out of the running for the Senate seat and is presumed to be headed for an administration post.

Blagojevich has said he would pick a successor to Obama before the end of the year. But the senator’s decision to resign his seat as of Sunday — a move made to avoid having to strike the difficult balance of serving as a legislator during the chamber’s upcoming lame-duck session while at the same time preparing to take over as the nation’s chief executive — will probably speed up the governor’s timetable.

That said, Blagojevich may want to savor the attention he will be receiving in the coming days and perhaps weeks.

After taking plenty of hits on ethics issues over the past year, a circumstance that caused many Democrats to distance themselves from the governor, Blagojevich will suddenly find himself to be very popular with the Illinois party’s more ambitious members.