it is really dependent on what era you look at.
Politics in the infancy of our country, really up to the civil war, were nasty. The handbill press savaged people personally. Jefferson's opponents tried to like him to incest and zoophilia. There was no decency in politics. And then the nation literally split and killed each other.
It seemed post reconstruction came with an implied civility (with noted exceptions). The union had proven fragile, and while the representatives of the states would fight hard for what they wanted, there was an understanding of the power of rhetoric, along with an understanding that they understood the pressures of the job like no other group of people. There was fraternity in that, and the characteristics of man at that time...to operate with tact, decency, and honor bled into their political dealings. The job was not so looked down upon.
A couple of things happened to get us where we are today...the Vietnam War and the media showing us what was actually happening sewed the first seeds of discontent among the general populous. The government was lying to us? Golf of Tonkin? Maybe the yellow journalism of yesteryear was more common than we thought? Is the government manipulating the message in this new era with this new medium?
Watergate broke the hearts of the people. We disagreed...sometimes violently. But now our president and his men were just petty crooks? And for such little gain? What did they do for the good stuff? That was the end of the innocence for those who still felt Vietnam was a necessary war to fight communism. Joseph McCarthy had been dismissed as a crackpot after his message became more and more crazy...even those who thought he was, at his core, right, just wrote him off as a loon. But now, we have the Vietnam War, Uncle Walter telling mom and dad that Vietman really was bad, and now our President is acting like a thug?
Carter had no chance. Reagan did serve one important role...talking real, real smooth and making those who wanted something to believe in have something to believe in. The switch of the southern Dem to the republican party is almost complete at this point, and the Democratic party becomes the party of civil rights, unions, and social programs. The right allies with the former southern Dems, and squeezes the last drops out of the cold war for the military industrial complex. We are regime building in central America, selling arms and maybe drugs to find covert operations (depends on whether you believe the Dark Alliance stories or not). This comes crashing down with some embarrassing scandals, but the Republicans have the weight with holding the former southern Dem, the conservative "Goldwater" republicans, barons of business, and now the working poor evangelical through the Moral Majority and Ralph Reed's entry into the world of US politics. But it was too much. Too many tents on the Republicans side, and something was bound to give...
Still, senators acted with some air of decency. But the Dems struck back with a centrist, a southerner who remained a Dem and could still carry that region in confusion while being on the good side of race relations. Clinton took the gooey center that was becoming less enamored with the evangelical driving the Republican bus. After 12 years of unchecked power in the executive office, the Clinton win shook the Reps up. They had dabbled with nasty play with Lee Atwater and the "Willie Horton" ads, but ultimately, Dukakis beat himself by climbing on a tank and essentially stopping his campaign with a big lead down the stretch. Now, the Republicans were ready to start firing the big guns. And that, rightly, started with the Contract with America and Newt Gingrich. Ralph Reed and the Religious Right got the evangelicals in line. And it became a game of "if you say this is a scandal enough, people will believe it is a scandal". Whitewater, Whitewater, Whitewater. Guy commits suicide...no, Foster was murdered. This coincided with the rise of the Right Wing Radio Host now that syndication was so much easier. The fringes could own the airwaves. Rush could hint that the CLintons were stone cold killers and people bought it. And out of a special prosecutor, we get Kenneth Starr, who found nothing about Whitewater, but got handed something so far out of the scope of the reason for his appointment, but because the special prosecutor had wide latitude, he used the Monica trap to catch the President lying about the answer to a question that NEVER should have been asked. That was not part of Whitewater. It was not important to the American people...It was a "GOTCHA", because they knew the answer, and got Bill to lie about infidelity, an impeachable offense.
That is when the world of politics really turned ugly. The Senate still had some decency, but the slide has been precipitous, with McCain having to bow to the loon side of the party with Palin, Michele Bachmann and her husband's Gay Cure, and so on. When a political figure actually started talking about Obama's birth certificate, that was the palest of the pale. But at least that was mostly TV wingnuts looking for attention, not actual politicians. Just some total loons.
Oh, wait...one of those TV loons pushing the narrative of Obama's "fake" birth certificate is our President.
And we lose...