**Arlen Specter, Democrat from Pennsylvania
*Biden spoke first at this morning's photo op, saying, "Arlen Specter has been my friend and my confidant and my partner and I his partner in scores and scores of major, major pieces of legislation. ... He's been there for me every time things have been tough for me, and I hope I have been there for him. And it gives me great pleasure to now officially be in the same caucus with Arlen Specter."

Specter repeated that he was unwilling to subject his record to the Republican primary electorate, and is "ready, willing and anxious to take on all comers" in the general election. He said Obama has projected an administration he's "comfortable with," and that he knows he can be helpful in sharing his views of "centrist government."

Obama spoke last, prefacing his remarks with talk about the swine flu (which he did not call swine flu). He called Specter one "tough hombre," and said he doesn't expect him to be a rubber stamp. "He has my full support, my full commitment to work with him on those areas where we do agree."

*Michael Steele, in an e-mail to RNC supporters: "When Benedict Arnold defected to the British, George Washington didn't fold the tent and give up either."

*Rush's reaction: "A lot of people say, 'Well, Specter, take [Sen. John] McCain with you. And his daughter [Meghan]. Take McCain and his daughter with you if you're gonna..." he told listeners, dissolving in laughter.

*VP Biden played a lead role in lobbying Specter to make the switch, pushing his friend for years. "I have been working on that in earnest for the past four years and double time for the past 100 days (as vice president)," Biden told a Democratic fundraiser in Houston on Tuesday.

*WaPo's Dan Balz: "How much more can the Republicans take? Demoralized, shrinking and seemingly lacking an agenda beyond the word "no," Republicans today saw their ranks further thinned with the stunning news" that Specter was defecting.

*VandeHarris: "Amid gloating among Democrats and recriminations among Republicans, the Specter divorce is both symptom and cause of the GOP collapse -- leaving the opposition party on the brink of irrelevance in Barack Obama's Washington and facing few obvious paths back to power."

*AP's analysis: "Specter's move ... is the latest blow to Republicans, especially in the Northeast, once a GOP stronghold. The region's Republicans now have been reduced to a scant presence in the House and a dwindling influence in the Senate. But Specter's defection has symbolic and immediate ramifications for the GOP nationwide. It makes it easier for Democrats, fairly or not, to paint the party as ideologically rigid and alien to large swaths of the country."

*Politics Daily's Carl Cannon writes that "two facts seem undeniable to me: First, the national Republican Party is indeed moving in a way that makes it harder for Northeastern moderates from "blue" states to keep winning statewide-just as the Democratic Party is moving to the left and making it hard for "red" state Dems. Secondly, when any of these dudes molt out of their old skins and into a new one, they are thinking first and foremost of Numero Uno."

*Politico's Charles Mahtesian: "The timing of Specter's switch came as something of a surprise in Pennsylvania, but the calculus behind it made perfect sense -- if the overriding goal is for Specter to remain a United States senator."

*Michael Barone: "Specter's argument -- that if a majority of Pennsylvania voters wanted him re-elected, he should be -- is obviously self-serving. But it's not self-evidently wrong. On conservative Web sites, the reaction seems to be "good riddance." I think this is wrongheaded, for reasons specific to Specter and more generally. Specter has not been a reliable Republican partisan, but when he has been, he has been mightily effective."

*NJ.com looks into the recent polls that forced Specter to switch sides, including the Rasmussen poll released Friday showing him trailing Toomey by 21 points.

*Politico's Josh Kraushaar: "It will be very interesting to see the first round of polling with Specter as a Democrat - reportedly the first polls are expected out this weekend. In the last Quinnipiac poll conducted in March, Democrats were the group most supportive of Specter, with 51 percent saying that he deserves re-election, and 28 percent saying they would not support him. A substantial 60 percent majority of Democrats viewed him favorably."

*Lou Jacobson: "Specter's sudden switch opens the field for more Republicans to challenge Toomey in the primary, while likely clearing the Democratic field for the five-term incumbent."

*Bill Pascoe, for CQ: "The moderate-to-liberal David Brooks-reading Republicans who form the core of the Pennsylvania GOP establishment aren't about to hand over their U.S. Senate nomination to the conservative Toomey. There's too much at stake, and it has little to do with a seat in the U.S. Senate."

*Sen. Olympia Snowe (R-ME) writes this NYT op-ed. "It is true that being a Republican moderate sometimes feels like being a cast member of 'Survivor' -- you are presented with multiple challenges, and you often get the distinct feeling that you're no longer welcome in the tribe. But it is truly a dangerous signal that a Republican senator of nearly three decades no longer felt able to remain in the party."

**100 Days
*Gallup's daily tracking poll finds Obama with a 65% job approval rating on his 100th day in office. "The new president's approval rating at the 100-day mark is notable in that nearly all major demographic categories of Americans are pleased with his job performance."

*AP reports that President Obama will mark the 100-day milestone "with two high-profile events, both designed to highlight the accomplishments of his fledgling administration." His trip to Missouri "is keeping in step with Obama's penchant for getting out of Washington." And the trip as well as the press conference is an attempt to control the message.

*"A gathering of good government groups ... banded together today to issue a joint statement to "praise President Obama for the unprecedented steps he has taken during the first hundred days of his Administration to strengthen ethics, lobbying and transparency rules for the Executive Branch," ABC's Tapper reports.

*John Harwood finds chief of staff Rahm Emanuel sounding pragmatic about the road ahead. "His goals are clear. He's willing to explore different roads to get to those ends," Emanuel said on health care and energy, in particular.

*Kyle's piece today: "For the first time since 1994, Republicans are the minority party in Congress while a Democrat runs the White House, and the transition has not been easy. Despite a mostly-unified party on both sides of the Capitol, Republicans' message of fiscal restraint and bipartisanship amidst a flurry of government spending over the last three months has not resonated with the general public."

*Washington Post's Balz says there has been nothing tentative about Obama's 100 days: "Some presidents start slowly. Obama began to lead even before he was sworn in, responding to a deepening recession by promoting an $800 billion stimulus package designed to prevent the economy from becoming even worse. He has set in motion so many initiatives -- domestic and international -- that his top advisers know that one of their biggest challenges will be to prevent the many pieces of his agenda from crashing into one another before they can be enacted and begin to work."

*Check out the long slideshow on the White House web site with some great behind-the-scenes photos from the 100 days.

**Other Campaign Stuff
*Specter wasn't the only former Republican making news: former-Sen. Lincoln Chafee (I-RI) made his candidacy for governor official, the Providence Journal reports.

*Former Republican Mark Parkinson became the latest Democratic governor of Kansas yesterday, after Kathleen Sebelius took office at HHS. He apparently is in no rush to name a new lieutenant governor, which could be an important pick since he's said he won't run for a full term in 2010.

*And in that now even more important Minnesota Senate recount, Gov. Tim Pawlenty made it clear that he'll sign a certificate of election if the state Supreme Court orders him to. Of course, the case won't be heard for another two months.

**Sports Alert: The Capitals defeated the N.Y. Rangers last night in an exciting 2-1 game, completing a 3-games-to-1 come-from-behind series win. Go Caps!

--Mike Memoli and Kyle Trygstad