It's Wednesday, so here's the next part!
Slade Gorton has also been junior Senator and senior Senator twice, and also served in both seats, but from Oregon instead of New Jersey. In 1980 he was elected with Ronald Reagan's help, defeating six-term incumbent Democrat Warren Magnusson (one of the most senior Senators to be defeated, rather than retiring; Ted Stevens holds the ultimate record of forty years between initial election and final defeat), but served only one term, nevertheless becoming senior Senator when Henry "Scoop" Jackson died in 1983, near the end of his fifth term. He wasn't done with the Senate, however, and managed to win election two years later, narrowly beating Representative Mike Lowry. Gorton continued with two more narrow reelections, being senior Senator after Brock Adams chose to retire at the end of one term (cough sex scandal), but Patty Murray beat him by 2,226 votes in 2000, and is currently serving.
Lastly, Kent Conrad has been junior Senator once and senior Senator twice, without ever leaving the Senate. He was initially elected in 1986, vowing not to run for re-election if the deficit did not decrease by the end of his term. The deficit did, indeed, increase, and he kept his vow; however, his colleague from North Dakota, Quentin Burdick, died in the early fall of 1992. Conrad decided that taking Burdick's seat didn't count as being reelected, and ran in the special election. The people of North Dakota apparently agreed, and he won. He resigned his first Senate seat on December 14, 1992, and Byron Dorgan was appointed to that seat the next day, having been elected to it a month and a half before anyway. Conrad and Dorgan have been serving together since then, but Dorgan retired in 2010, and was replaced by John Hoeven, the immensely popular sitting governor, who beat Tracy Potter by fifty-four points. Conrad himself announced his retirement in early 2011, and though it's anybody's guess who the candidates on each side will be, right now it's pretty much the Republicans' to lose.
Arlen Specter was originally a Democrat, serving as Philadelphia's assistant District Attorney. He ran for DA itself on the Republican ticket as a registered Democrat, most likely because the Republican primary was easier to get through. Specter beat the incumbent Democrat easily, and served two terms as Phillie's District Attorney. In 1976, he tried to primary John Heinz, Pennsylvania's senior Senator at the time, and lost; in 1978, Dick Thornburgh beat him in the Republican primary for Governor of Pennsylvania, and subsequently won the general election. In 1980, he finally managed to win a Senate seat, and served mostly without incident until 2004, when former Representative Pat Toomey ran to his right in the Senate primary; Toomey lost 51-49, and assumed the chairmanship of the Club for Growth, which had helped to bankroll and publicize his attempt. After the contentious 2008 Democratic primary, in which season Pennsylvania came fairly late - before it was clear Clinton could not win, but after it was clear that Obama was gathering momentum - many moderate Republicans switched their registrations to Democratic so they could vote in the interesting primary. McCain had long since wrapped up the Republican nomination, not that Huckabee or Paul would admit it; interestingly, McCain regularly got around 75% of the primary vote, meaning that a substantial chunk of people went out to vote against him even though he'd essentially already won. In any case, Specter's base, which had carried him to very narrow victory in 2004, was mortally wounded.
Acknowledging his poor primary polling numbers, as well as his ideological distance from the Republican Party, which had been growing for years but especially quickly as the GOP radicalized after the 2006 and 2008 elections, Specter officially changed his party registration in spring 2009, having already voted for the budget and the stimulus. Specter's move saved him from a harsh GOP primary, but as his rhetoric drifted oddly to the right, he eventually gained another primary challenger, sophomore Rep. Joe Sestak, a former vice-admiral in the Navy. As Specter continued to whine and generally not vote like a Democrat, Sestak's primary numbers rose, though he was never at the point of beating Specter; eventually somebody hit Specter with a clue-by-four, and he started voting the way the people who would be engaged in the Pennsylvania Senate Democratic primary wanted him to. Through all of this struggle on the left, Toomey wisely shut the hell up and let Specter and Sestak trash each other; as a consequence, their numbers sank and his stayed about the same, though he wasn't able to take that strategy after the primary. On May 18, 2010, Joe Sestak became the Democratic nominee. Well done, Arlen. For virtually the entirety of the campaign afterwards, Toomey led Sestak, though rarely by more than five or six points, and ended up beating him by just two. Sestak gave up his House seat, which was taken by a Republican, but he's only 60, so it's quite possible that he'll return to politics in the future. Or at least, I haven't heard of him taking a lobbying job, which is usually a clincher, people like Dan Coats notwithstanding.
Richard Nixon. Oh, Richard Nixon. He was the closest anyone has ever come to serving two terms as Vice President and two full terms as President, being forced to resign a little less than halfway into his second term for being a slimy sleazebag crooked son of a bitch. Not that I'm biased. In any case, his Vice President, Spiro Agnew, about whom more later, resigned in late 1973 under charges of various financial crimes while governor of Maryland (Agnew, incidentally, had the fastest rise of anyone in politics pretty much ever: he went from Baltimore County Executive to Governor of Maryland to Vice President in six years), so Nixon needed a new one. He chose Gerald R. Ford, the minority leader in the House of Representatives, who was moderate enough to get by the Democrat-controlled Senate; this proved fortunate, because Nixon himself needed to be replaced in August of 1974. Ford became the first (and so far, only) unelected President, which he acknowledged in his first address to the nation, and pledged to work to be everybody's President, instead of just, say, Michigan's. (Ford represented Michigan's 6th district in the House.) Naturally Ford needed his own Vice President, and he chose Governor Nelson Rockefeller of New York, another moderate who could pass the Senate, who was willing to resign from his fourth term as governor, and was confirmed in December of 1974. Rockefeller had run for the presidency in 1964, and had a good chance of getting the nomination, so he might have had hopes of succeeding Ford, but you'll find out about that in just a bit. In between Ford's succession to the Presidency and his selection of Rockefeller, there were midterm elections. As you might have guessed, Republicans did not do well. The minority lost 49 seats in the House, ending up with 144 out of the 435 seats, while Senate Republicans lost much less but still ended up with fairly little, having a net loss of four seats and retaining 38 out of 100 in the Senate. Ford eventually decided to run for his own term as President in 1976, and chose running mate Senator Bob Dole of Kansas, who, as you may recall, was the Republican Presidential nominee in 1996, and did significantly worse against Clinton than he and Ford did against Carter. The age gap between Clinton and Dole in 1996, 23 years, was the greatest up to that point, but was exceeded by Obama versus McCain, with 24 years.