Republicans and Democrats wasted no time Saturday welcoming Sen. Joseph Biden (D-Del.) into his new role as Sen. Barack Obama’s (D-Ill.) running mate, with Republicans using Biden’s critiques of Obama in ads and public statements while Democrats – and some Republicans – praising the selection.

With Congressional approval ratings at record lows, Obama’s decision to select Biden flies against conventional wisdom on a number of fronts. First, it is unusual for two Senators from the same party to run for president and vice president. Furthermore, Biden hails from a small, Democratic mainstay state in the Northeast and not from the South or West, areas where Obama is hoping to pick up support. Finally, Biden is in many ways a mainstream Democrat who has served in Congress for 38 years instead of a conservative Democrat from outside the Beltway.

The selection of Biden, chairman of the Senate Foreign Relations Committee, could also spark significant changes in the top tiers of the Senate next year, particularly if his next in line on the Foreign Relations Committee, Sen. Chris Dodd (D-Conn.), decides to take the reins and vacate the chairman’s seat on the Banking, Housing and Urban Affairs Committee.

But for Saturday, Democrats were squarely focused on painting Obama’s choice as a tough, straight-talking foreign policy expert with strong bipartisan chops.

“Joe Biden has been fighting his entire career for the change that Sen. Obama champions. He is a dedicated family man who has been an effective chairman of both the Foreign Affairs and Judiciary committees, has been a sage voice on many of the toughest foreign policy issues of our time, and has long been a strong advocate for protecting American families and making our communities safer,” Senate Majority Leader Harry Reid (D-Nev.) said Saturday morning.

Democratic Senatorial Campaign Committee Chairman Charles Schumer (N.Y.), an early supporter of Sen. Hillary Rodham Clinton (D-N.Y.) in the presidential contest, called Biden a “class act” who unlike many politicians can communicate with average Americans. “Joe Biden knows how to talk to average folks. He has a rare gift of talking straight,” Schumer said.

Reid also penned an e-mail fundraising pitch for the Democratic Senatorial Campaign Committee, urging supporters to pony up funds to “not only … put Barack Obama and his running mate, Joe Biden, into the White House, but we’re going to elect a filibuster-proof Senate majority that can and will pass the Democratic agenda.”

By mid-morning, the presidential campaign of Biden colleague Sen. John McCain (R-Ariz) had already launched an ad that uses archival footage of Biden criticizing Obama’s lack of experience to underscore the GOP argument that the Democratic nominee is little more than a celebrity with a thin résumé.

Likewise, House Minority Leader John Boehner (R-Ohio), whose Conference has been engaged in a weeks-long “protest” on the House floor over gas prices, argued that the Democratic ticket would do nothing to help solve energy and economic woes.

“Americans looking for a pair of candidates who are ready to fix a broken Washington aren’t going to find them on the Obama-Biden ticket. In Joe Biden, Barack Obama has not only found a running mate who doesn’t believe he’s ready to be president, he’s proven his opposition to an ‘all of the above’ energy-reform strategy to lower fuel costs for families and small businesses,” Boehner said.

But despite the immediate attacks on Biden by Republican leaders and McCain, he also drew strong praise from a handful of Republicans, adding to the unusual nature of the Biden selection.

Former Senate Foreign Relations Chairman Sen. Dick Lugar (R-Ind.) Praised Biden for taking a bipartisan approach to foreign policy issues. “I congratulate Senator Barack Obama on his selection of my friend, Senator Joe Biden, to be his vice-presidential running mate. I have enjoyed for many years the opportunity to work with Joe Biden to bring strong bipartisan support to United States foreign policy,” Lugar, who was rumored to be under consideration for the vice presidential slot by Obama, said in a statement.

Sen. Chuck Hagel (R-Neb.), who was also a rumored possible running mate, also hailed the selection. “Joe Biden is the right partner for Barack Obama. His many years of distinguished service to America, his seasoned judgment and his vast experience in foreign policy and national security will match up well with the unique challenges of the 21st century. An Obama-Biden ticket is a very impressive and strong team. Biden’s selection is good news for Obama and America,” Hagel said.

Senior Democrats said Biden would remain on this year’s ballot for Senate in Delaware, meaning at least for now the musical chairs won’t begin for at least several months, if at all.

But should Obama and Biden win, it could result in some behind-the-scenes maneuvering. For instance, Dodd, whose state is home to a number of banking interests, could opt to remain chairman of the Banking Committee. But in recent years, Dodd has become increasingly vocal on foreign policy issues, and became the champion of privacy proponents in their fight against the Bush administration’s wiretapping program. Several Democrats have speculated he could opt to take the gavel of the Foreign Relations Committee.

If Dodd does move, and assuming he wins his own campaign as expected, Sen. Tim Johnson (D-S.D.) is next in line for the chairman’s seat on Banking. Democrats close to the issue said Johnson would almost certainly take over the panel, pushing the senior South Dakotan into the upper levels of the Democratic leadership despite recent health problems.

Should Dodd remain on Banking, Sen. John Kerry (D-Mass.) is expected to take the helm of Foreign Relations.