Testifying for the first time in a criminal case, Sen. Bob Casey said Thursday that Rep. Chaka Fattah sought to enlist his aid in 2008 to land a White House appointment for a wealthy, politically connected lobbyist.

But the Democratic senator maintained, speaking to reporters after a brief stint on the witness stand in Fattah's federal corruption trial, that he knew nothing of bribes that prosecutors now say bought the congressman's support.

"We received a lot of requests - in most cases from the individual" seeking appointment, Casey told jurors of a letter Fattah wrote him lauding lobbyist Herbert Vederman's qualifications. "But this request was for an ambassadorship. You don't get many of those."

Casey, whose testimony came as the racketeering conspiracy case concluded its second week, is the highest-ranking Washington official to appear in nine days of testimony.

The jury has heard from a string of program administrators from various federal agencies that awarded grants to Fattah-backed nonprofits. On Thursday, a representative from the Federal Elections Commission walked the panel through years of the congressman's campaign finance filings.

But Casey's midday arrival in a white SUV at the federal courthouse on Market Street set off a flurry of activity on an otherwise routine day.

FBI agents escorted him into the courtroom, interrupting testimony from another witness to accommodate what U.S. District Judge Harvey Bartle III described as the senator's "tight schedule."

After spending less than 20 minutes on the stand, Casey told reporters afterward he was happy to share what little he knew.

Prosecutors have accused Fattah and Vederman, who also is charged in the case, of participating in a bribery scheme that lasted years. In exchange for cash gifts as well as college tuition payments for Fattah's au pair, the congressman allegedly worked tirelessly to fulfill Vederman's ambitions to secure a White House posting.

Casey, an early Barack Obama supporter who held a seat on the Senate Foreign Relations Committee, said he received nearly 200 requests in late 2008 from people seeking appointments in the administration.

He told jurors that he had met Vederman, a prominent Democratic fund-raiser and former deputy mayor of Philadelphia under Ed Rendell, years before Fattah's letter. But the two often found themselves on opposite sides of political fights.

Vederman backed Rendell in the 2002 gubernatorial race, in which Casey also had run as a potential Democratic nominee.

When he received Fattah's request in the days before Obama's inauguration, Casey said, he was not inclined to help.

"As for making a specific step to recommend [Vederman] for an ambassadorship," he testified, "I wasn't prepared to do that."

Vederman had contributed $1,500 to Casey's 2006 reelection campaign. But after taking no action on Fattah's 2008 letter, Casey said, he received an icy greeting from Vederman when he called again in 2012 to ask for the lobbyist's support.

"He expressed not just disappointment, but real frustration, on not being appointed," Casey said. "But that tends to happen in these situations."

Fattah, however, was not deterred, prosecutors say.

Two years after contacting Casey, Fattah allegedly pressed a letter touting Vederman into the hands of Obama himself.

Kristen Sheehy, a former White House scheduler, testified Wednesday that the congressman's office also repeatedly pushed her for a meeting to discuss a possible appointment with the president's then-chief of staff, Rahm Emanuel, or Emanuel's deputy Jim Messina.

"Mr. Vederman is willing to serve in any location that is helpful to the Obama administration," read one letter Sheehy received. Another touted Vederman's willingness to work for an annual salary of $1 in various positions under Rendell.

"He now offers his service to the president for the same sum," it noted.

Vederman's lawyers have argued that their client was not just a wealthy lobbyist but also extremely qualified for an ambassadorship. He was frequently part of delegations to Europe and Asia as a deputy mayor and served as an adviser to the Center for Global Peace at American University.

His lawyer Robert Welsh told jurors last week that what prosecutors have taken for bribes were actually gifts between his client and Fattah, a longtime friend who would have backed Vederman's ambitions without them.

"Mr. Vederman is a self-made man who retired at a very young age and has basically committed himself to public service," Welsh said. "These two people might be considered the odd couple of politics."

Aside from the alleged bribery scheme, Fattah is charged with misusing campaign funds, charitable donations, and federal grant money under his control to pay off debts and advance his career.

Testimony in the case is expected to resume Tuesday.

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