THIS IS NOT your father's Jesse Jackson.

U.S. Rep. Jesse Jackson Jr., D-Ill., has gained elective office - something his civil-rights icon father has never done - while occasionally clashing in public with his controversial dad and embracing the wonky issue of a new airport for his Chicago district.

But the 43-year-old junior Jackson's speedy political rise - which appeared destined to take him possibly to the U.S. Senate or beyond - hit a gigantic speed bump last night as questions continued to swirl about his possible dealings with disgraced Illinois Gov. Rod Blagojevich.

Jackson and his attorney confirmed yesterday that the civil-rights scion is Senate candidate "No. 5," a politician that Blagojevich believed would be willing to "pay-to-play" in order to win the corrupt governor's appointment to take over the seat vacated by President-elect Barack Obama.

Jackson's denial was forceful.

"I did not know that the process had been corrupted," Jackson said at a news conference yesterday. "I did not know that credentials, qualifications and record of service meant nothing to the governor. I did not know that the governor and his cronies were attempting to use the process to extort money and favors in a brazen pay-to-play scheme."

Still, the simple fact that Jackson's name and the possible actions of his allies surfaced after Tuesday's arrest of Blagojevich seems to have all but doomed the congressman's chances of replacing Obama and running for a full Senate term in 2010.

Before the stunning news about the governor's arrest, political experts had said that Jackson had the highest Illinois name recognition of the hopefuls and would certainly have a shot at an appointment, especially since Obama's departure leaves the Senate now with no African-Americans.

Despite his denials, Jackson's path to higher office remains less certain today.

"He's damaged," said Larry Sabato, the University of Virgina historian and national political pundit. "I don't know if he's toast, but he's damaged." He said that Jackson's name being linked to the probe makes it unlikely that he'd be appointed, and if there is, instead, a statewide special election, the scandal gives downstate Illinois whites an excuse not to vote for him.

"He's no Barack Obama," Sabato added.

The questions about the junior Jackson arose within minutes of the release of the criminal complaint against the two-term Illinois governor, who was arrested in his Chicago home before dawn on Tuesday. He was arrested even before the case was brought to a grand jury to stop what prosecutors called "a political corruption crime spree."

The documents said that wiretaps placed on Blagojevich showed that in late October, when it appeared that Obama was on the way to the presidency, the governor spoke of a conversation with emissaries for candidate No. 5, now confirmed as Jackson.

"We were approached 'pay to play,' " Blagojevich said, according to the court documents. "That you know, he'd raise me 500 grand. An emissary came. Then the other guy would raise a million, if I made him a senator."

The criminal complaint also implied that Jackson - who was an ardent supporter of Obama in the presidential race despite Jesse Jackson Sr.'s well-documented harsh words for the now-president-elect - was not Obama's choice to replace him. The complaint said that Blagojevich spoke of using the threat of naming Jackson to extract favors from Obama.

"I thought - mistakenly - that the governor was considering me based on my 13 years of working on behalf of the hard-working people of the state as well as the nation," Jackson said yesterday.

"I thought - mistakenly - I had a chance and was being considered because I earned it."

It is a bizarre end to a tumultuous year for Jackson - who publicly clashed with his father and accused him of "ugly rhetoric" after Jesse Jackson Sr. disparaged Obama over an open microphone. Politically, the younger Jackson holds liberal views but is seen as less of a fiery orator and more of a policy wonk than his father, who amassed considerable support in 1984 and 1988 presidential bids. *